I see you're giving Tempest a look. To that I give a resounding "eh". You're better off with Ranger and Fighter levels leading to a different PrC, as most things the Tempest can do ranger/fighter can about as well. Strangely, the two main abilities of the class cancel each other out. At higher levels, you'd be giving up 3 (or 4) off hand attacks for a small AC bump? Not worth it. Also, the only ability you can't duplicate with standard feats is perfect ambidexterity which is only a +2 to hit. Again not significant at high levels.
IMO strong prestige classes for a fighter:
Fighter/Divine Champion/Holy Liberator is a great choice, especially with the Det Evil and immunity to charms and compulsions. Put some points into Cha and you've made a quite self-sufficient front liner with added punch when needed.
If you really want to break out the funkiness:
4 Fighter/3 Rogue/X Lasher. THe higher level abilities of the Lasher class are sick. Fight 2 handed with a Defending Dagger, a Buckler and Off Hand Parry, your AC will shoot to the moon. If you can manage the feats, eventually try for Duelist. That's a tough one though.
Knight of the Chalice is also pretty sweet but it's too specialized.
One of the most useful classes out there for fighter/ranger types would have to be Planar Champion. It's easy to qualify for and has abilities that are indispensible. The ability to see invis, turn one or both of your weapons into force effects (for an unlimited time!) and the ability to open/sunder portals can all be total party lifesavers. If your DM allows it TAKE IT.
Good to hear that you have a cleric, otherwise I would've recommended going for a 1 Ranger/6 Cleric/X Windwalker, using a Duskwood Keen Greatsword (for Spikes spell) and armor spikes for off hand attacks. Combine this with the mobility (Air Walk) and fighter BAB of the Windwalker, and cast spells as a cleric of one less than your level? Ouch. You know what? I recommend this one anyways.