Microlite20, the ultra slim version of the d20 SRD, has been available for some time now, and it has been modded up and down so many ways that you can find a hundred different games using the same basic ideas, from westerns to space operas. It's nice, I've played it, but it wasn't until I sat down this last weekend and gave a version called Microlite74 a try that I truly appreciated its flexibility.
Designed by Randall Stukey, Microlite74 is a game with the familiar d20 conventions, but with an old-school flavor. Coming in three distinct booklets, each with a small overall page count, you can enjoy Microlite74 Basic, Standard, or Extended, each playing under different assumptions.
In Basic, you can play as Humans or the classic three Demi-Humans (Elves, Dwarves, Halflings) and there are three character classes, the Fighter, Cleric, and Magic-User. That's right, no thief (or rogue for those politically correct 3e players).
Standard increases the player races and classes, adds some extra combat rules (firing into melee, allowing a shield to be destroyed to negate all damage, etc.), and adds a bunch of new spells.
Extended has even more rules for combat, an alignment system, adds even more classes (Warlord? New bestest class ever?) and plays more like a trimmed down 3.5 than a modernized B/X.
And, included with these three rule subsets is a well-written book of variant rules. Optional rules like Vancian magic, a virtue system, a catch-all Adventurer class (recommended for swords and sorcery games), and even a basic Feats system and Psionics rules, each recommended for a different version of M74.
Overall, it's a charming package, well-written and clearly well-tested. The newest revision came out on October 1st and I did my best to scrounge up a quick game as soon as I was able. Gameplay was exceptionally easy to get into, although there was some unease about the idea of Magic-Users employer their HP to cast spells. In practice it worked very well, replacing that severely limiting per-day casting ritual with a more organic flow, yet still retaining most of the tension about whether or not to spend the HP now or later.
I ran Standard with some of the variant rules in the M74 Companion and it was very reminiscent of B/X with more of a modern flair in certain aspects, which my group liked a lot.
It won't be taking over our regular campaigns any time soon, but I might use it for my next play-by-post game, thanks to its availability and ease of use. I'm also thinking of having it replace B/X (through the Labyrinth Lord retroclone) as the game I use to introduce potential new gamers into the hobby.
And if you really enjoyed it, or just have a fondness for TSR-era D&D and a penchant for a decent cause, you might want to consider making a donation to Randall Stukey's cancer drive; he's offering some old TSR-era goodies for the highest donors.