It seems to me you have a few options that would be useful for you:
1. Continue a feat chain
You have Power Attack and Cleave: Great Cleave seems like an obvious choice. However, Great Cleave is DM dependent on its usefulness. Does you DM have encounters with multiple lower powered enemies? If he is only throwing the BBEG's at you all the time, you will never get to use it.
You also might consider Power Critical considering your obvious focus on the great sword. The yield for this feat for a great sword is not as great as it would be for a Pick or Scythe, but the feat could still let you dish out some massive damage. You also have Power Lunge. I don't remember off the top of my head whether or not there is a feat that requires that as a pre-req, but if there is, you might want to take it.
Finally, you might want to consider Improved Bull Rush or the Sunder chain. Improved Bull Rush is an often overlooked feat as people usually think its usefulness is limited to pushing opponents into dangerous areas like off cliff edges or into spiked walls, etc. However, Improved Bull Rush is deadly if you have a team. If you all work together and you can manage to position yourself to push your opponent through your enemies threatened areas, you will subject your opponent to many AoO. This is especially if you have a rogue in your party opposite another ally and you can push your opponent inbetween the two - flanking rogue with AoO deals SA. The use of this feat requires all players to be tactically savy. I am not sure of your groups experience level (in terms of time gaming with 3E) but if they are good, this is a great tactic - especially since you are strong and can get stronger with the rage.
Sunder is a double edged feat. It is great as you will be able to trash most weapons especially if you take improved sunder with it (with your second feat). But the drawback is that you destroy a weapon your group could possibly have used in the future. That is more of a rollplaying constraint and in terms of roleplaying I don't think ought to really be considered. However, it does deplete - on average - the amount of treasure you get per encounter. If your DM will be nice and make up for this somehow, then all the power to you...but not all DM's are nice

.
2. Take a feat which augments or has synergy with your other abililties.
You have 4 things going for you: your combat ability derived from high strength and focus on the great sword, your increased speed, your high hit points, and your charging ability (with power lunge). You also have one serious drawback: your low AC which is worsened when you use one of your strengths - charging.
With your high strength and damage dealing potential. but reliance on large weapons, grappling ruins you. Close Quarters Combat may be a good choice. Again, this is DM dependent, however. If you never see any dire Bears, Dragons, or the various (and increasingly common with MM2) creatures with improved grab/grapple, then the feat really will not be too useful. This would be something to talk to your DM about ahead of time.
You also might want to consider Extra Rage. It effectively gives you the ability that a few levels of Barbarian would which on a level for level basis gives you a positive gain. Also, this feat is more powerful the lower level you are in barbarian. Since you are only first, this feat will be very useful. The other rage feats might also be useful - at least consider them.
You could always go with one of the hit point raising feats. I think you would only qualify for Giant's Toughness if my memory serves, but still, the extra 9 hp (probably the equivalent of 1 hit dice) can save your life. I personally would recommend going with an AC raising feat, however (discussed below).
Your charging ability is really powerful but has the serious drawbacks of lowering your AC (and if also raging - well that's just nasty) and also PROVOKING AN AOO. It seems that the clear thing to do is get something which improves your AC. Dodge seems like an obvious choice and also helps with the pre-req's for Spring Attack (discussed below). I would also recommend Armor Focus Breast Plate (armor focus is from Rokugan - gives you a +2 AC with specific armor). If you can manage to get your hands on a Mithril Breast Plate, you would still retain your max speed and have a very nice AC. With the armor focus you get an additional unnamed +2 bonus. Enchant the armor and suddenly your AC is on par with your other fighter types. I can't think of a way to get rid of that AoO and still make use of your other abilities, but if you can, embrace the idea. Other than getting rid of the AoO, I would say increase your AC.
You could focus also focus on your mobility and go with the Spring Attack feat chain. This may seem like more of an exchange of power than increase to it. However, consider this: while you will not get your subsequent attacks, you also deny your opponent from getting theirs (as they will have to move to get to you). Spring attack would also increase your versatility giving you the option of not sticking around (considering your low AC). Finally, (especially at later levels) you are probably going to be facing more opponents with reach. This gets rid of that benefit.
The best thing about the feat chain are none of the above benefits however. Rather, it is the two feat prereqs that are the benefit. As stated earlier, Dodge will be useful because of your low AC. But Mobility is simply a boon. The +4 AC will be tremendously useful if you want to get to a particular opponent but have to move through other's threatened area. This will have great synergy with improved bull rush if take it as well as Power Lunge (so you can not have to worry so much about the charged opponent's allies). I do not know if there is any errata out there, but if the AoO from Power Lunge is considered a movement based AoO (if I were a DM, I would rule it was). If it is, this suddenly counteracts the AC penalty while raging.
Take a feat that counteracts your weaknesses.
I already went into detail about Dodge, and Mobility - both of which can be very useful. As an aside, Mobility, much like improved bull rush, is an often overlooked feat - usually considered as simply a worthless prereq to get the powerful Spring Attack. This view is woefully mistaken under the right circumstances. If, AND ONLY IF, you can get your AC fairly high Mobility is a great way to draw AoO from enemies to give you and your allies options when attacking. If you circle your opponents with your 40' move taking AoO from them, and they do not have Combat Reflexes or any of the other abilities increasing the number of AoO one gets per round, then when you make your attack or partial charge, or your enemies make their attacks, they have the option to do special maneuvers which provoke AoO and not have to suffer them. This is especially good with: monstrous spell casters that would hit with their AoO against a grappler, disarming an opponent - especially for you with your high str and greatsword and inability to take expertise, etc, sundering, giving allies the ability to move unmolested, etc.
I would definitely weigh heavily your low AC and try to make up for that somehow. This will also be more useful than more hit points. More hit points are certainly great and will make the difference when you get low. However, if you can reduce the overall amount of damage you take, each hit point becomes relatively more valuable and with already high hit points and low AC, it seems to me that the low AC is where you should focus.
Iron Will, would be another good choice as your Will save probably sux. I would also go with Iron Will over Lightning Reflexes as you could probably soak the damage from the reflex saving throw spells, but getting charmed/suggested to/dominated/held/etc. would be devastating.
Close Quarters Combat is described above.
Blind Fight - always a good choice - very good if your wizard friend casts darkness on you and you charge. Suddenly that AoO has a 50% miss rate where as your attack only gets a 25%. Also, if you charge the enemy spell caster they can no longer see anything and subsequently can't target spells.
If I were you I would go with Dodge and Mobility as my two feats and get Improved Bull Rush with my next feat - but that is just me

.
Hope all that helps.