- Magic weapon
- Magic armor / shield
- Ring of Protection
- Amulet of Natural Armor
- Cloak of Resistance
- Ability score booster for your primary stat (or stats)
- Gloves of Dexterity or Gauntlets of Ogre Power / Belt of Giant's Strength for physical classes
- Headband of Intellect, Circlet of Charisma, or Periapt of Wisdom for casters
There's a lot of complaining about the Big Six because they're optimal, but boring - you never have to activate them, they don't do neat things, and generally they go one your character sheet, you add the bonus in to your stuff, and then you forget about them. I've addressed this previously and at more length here.
3.5 reserve feat source: Reserve feats first appeared in Complete Mage, but there were also several in Complete Champion, I believe (including one that provided free healing up to half of the recipient's maximum HP, which was quite nice for taking a really torn-up party and bringing them back up to some semblance of fighting shape). They were a neat idea, but some of them were not particularly well thought out. Since it looks like a similar mechanism will be core in 5e, I'm hoping they'll do a better job there.
Base magic bonus: In Trailblazer, base magic bonus is a measure of a character's total magical prowess, much like base attack bonus is a measure of their fighting ability. BmB serves as your caster level for all spells that you cast. It's also how TB managed their elegant solution to multiclass casters; BmB from multiple classes stacks, but the maximum level of spell you can get from a particular class' spell list is limited by your total BmB from the class. Fighters, Rogues, and Barbarians have 1/3 BmB (so +1 for every 3 complete levels), while Monks, Rangers, and Paladins have 1/2 and full casters have 1/1. Bards have 2/3 with an odd caster-level hack. As an example in usage, a Fighter 6 / Ranger 4 would have +4 BmB total; +2 from his six fighter levels, and +2 from his four ranger levels. Since he has +2 from ranger and an effective caster level of 4 total, he can prepare and cast 2nd level spells from the ranger list (though TB actually has them using the Druid spell list).
Similarly, a Sorcerer 3 / Cleric 3 has BmB +6, and 3 from each class, so he can prep and cast 3rd level spells from both lists. When he levels, though, and becomes a Sorc 4 / Clr 3, he can now cast 4th level spells, since he has BmB 7 and hence 7 caster level... but only from the Sorcerer list, since he doesn't have 4 points of BmB from Cleric. I refer you to Trailblazer itself for further information, and my 3/4 BmB full-caster hack, should you decide against using action points.
fun magic items for first level characters: Not something I've ever investigated thoroughly - at first level, every magic item is fun (well, unless it's cursed). Al wrote up a few a while back, though; while they're nominally for old-school usage, they'd work OK in 3.x except for the thieves' tools, which you could easily swap out for masterwork thieves' tools per the SRD.
OSRIC random dungeon: I may not be the most qualified to speak on this, since I only ran one session in it, but I did generate a random dungeon under OSRIC's rules. My roommate has also done so (and more extensively than I), and I believe wrote a program to help with it by generating room contents... Overall, I'd say that the random map generation is fairly weak (but it always is), while the random room contents are pretty good. If I were to populate a 'random' dungeon, I'd probably pop on over to Dyson Logos', borrow one of his many many excellent maps, and then stock it with the OSRIC room contents tables. Wizards' old map of the week archive might also have some good ones; I haven't been through there thoroughly in a looong time.
OSRIC introductory adventure: Sadly, I can't say I've found one yet. Free intro module support in the OSR seems to be fairly weak, as Al of Beyond the Black Gate discussed way back in '09. In other news, maybe I should write one for ACKS... OSRIC as a system, while interesting, is more complex and less to my tastes (and, I suspect, those of my players) than ACKS.