Some other thoughts on how to make the wizard feel useful:
1) There are certain types of creatures that are especially upsetting to melee types because of DR or force effects. Throwing some of those at a party might be a good idea (although it's important to note that you should figure out if they'll know it's susceptible to force effects first.) This was actually one of my beefs with being a *fighter* in 3.0--with the 3.0 DR system, we came up against things with DR better than my weapon and I ended up being the distraction while the wizard plinked away with magic missiles and the like.
It's not quite as big an issue in 3.5, but there's still some potential for threats that a wizard can deal with more easily than a fighter can.
2) That leads to my second thought: In my opinion, any Wizard worth his salt should have reasonably high Knowledge skills in a variety of subjects. When the big tentacled beasty that they've never seen before pops up out of nowhere, do an appropriate Knowledge check and give the wizard a note giving some info on the critter. While a Druid might identify natural critters better, or a Cleric identify undead better, a Wizard can be expected to know about a wider variety of things. (And even if he doesn't, you can throw some creatures where Knowledge (Arcana) applies. I *do* hope he has Knowledge (Arcana) trained.)
3) Crafting scrolls is a very very powerful thing for a wizard. If the party is barely slowing down to breathe, it's almost certainly not slowing down for the wizard to replenish his stock of scrolls. A first level scroll costs 1xp and 12gp to make. By the strict reading of the rules, you can only make one a day, but there are various optional rules to make this work better in low-downtime campaigns (crafting points from UA are a good one.) The simplest one I can think of is this:
You can craft items up to a value of 1000gp in a single day, but of course you're still limited by your memorized spells. So a third level wizard could request a day of downtime, memorize his 3 first level and 2 second level spells for the day (assuming he's not a specialist), and whip out five scrolls easily. If second level spells are too pricey (6xp, 75gp each), memorize first level spells in those second level slots to do this trick. Some great ways to use scrolls would be for extra combat spells, for spells you cast pretty much every day (mage armor, anyone?) to free up those spell slots, and spells which are very handy on occasion, but not always. (Detect Secret Doors, Detect Undead, Comprehend Languages, Animate Rope as a sampling of first level spells that might fall into that category.)
A wizard's great power is versatility, backed up by the ability to create spell trigger magic items for those spells that need to be used all the damned time. Allowing time to craft those items is a big big help to any wizard.
3) In the worst case, Wizard might not actually be the class best suited for him, even if he likes arcane spellcasters. While learning about specific options wizards have for flexibility could help, if he's a more in-your-face style player, he might find that he'd enjoy the Sorcerer class much better. Sorcerers don't have anything approaching the flexibility of a Wizard, and they get the hard-hitting spells a little later, but they have much more staying power than a wizard does, as far as casting casting casting goes. On the minus side, they don't get Scribe Scroll for free, and even if they did, it's not as useful. A sorcerer needs wands and scrolls to provide the spells he can't cast, not to increase the number of times per day he can cast. Anyway, that's a thought.
But I suspect that with the suggestions everyone has shared, and maybe the opportunity to judiciously adjust ability scores and skills based on a better understanding of what is and is not useful to a wizard in 3.5, he should end up happier. In fact, in a level or two it might be worthwhile to spend a little gameplay downtime with everybody and see if "tuning up" the party based on things people have learned would be a good idea. The rules in 3E are very consistent and nice, but some of us who've been playing it for a long time sometimes forget just how many options there are. There are lots and lots of different effective characters you can build--but until you see the rules in action, it's easy to miss one ability or another that can really make a difference. (Like not thinking of Knowledge skills for a Wizard, or not thinking about scroll-making, or not realizing exactly how important Concentration is for spellcasters.)
Oh, and a final suggestion: you have the power to make downtime happen more often.
If your players have been romping through at so great a rate that the wizard is out of spells and everybody else is still ready to zoom forward, I'd say that there's a good chance that your melee types aren't getting hit hard enough. (Although a wizard who uses every one of his spells in a single combat where the other characters are whizzing through doesn't help.)
And make sure to set up situations that will reward new tactics that you introduce to your wizard. If he starts leaving a slot free, throw in an encounter where the party has the jump on the enemy, and where one of his spells will provide a tactical advantage. For example, a bunch of critters that are individually weak but could be a serious flanking hazard in a group. If he then sits and grabs sleep or web, this will turn things very much in the party's favor. Likewise, if he becomes more willing to burn charges in the wand, throw something up against the party that is ethereal or blinking or displaced or has damage resistance that your fighters can't defeat easily--lowish hit points, but hard to actually do damage to. The tough guys will take the brunt of the damage while he peppers the enemy with the wand to good effect.
All in all, wizards do really have it rough in the early levels. Mainly because the low number of spells per day combined with few spell levels makes leaving spell slots empty very painful. When you have three levels and a few spells at each level, leaving an empty first level or second level slot isn't bad. When you only have five spells total per day, it's much harder to think of doing that. This sort of thing, along with the utter lethality of low levels to an average party's characters, is one reason that I usually start at least at level 3.
Good luck!
, he has also suggested that he finds it difficult to work with.
