I have a new addiction. No, not pills. That's reserved for the next decade. No, my addiction is racing games. I made a big mistake downloading a few racing games for the Mac, and I thought I'd share them and turn you into wasted, glassy-eyed junkies, too. The three games are TORCS, VDrift, and Dolphinity Racer. The first two are open source, and all three are freely available for OS X as well as other platforms. They all have their pros and cons and are different enough to make you want to play all three. I tested these on a 1.5 GHz AlBook and a Sawtooth with an ATI 9000 upgrade. So here's the round up:
Dolphinity Racer is the most graphics and processor hungry of the three. The latest for OS X is v0.5.4.3, which is a universal binary so it'll work on PowerPC. Unfortunately the developer hasn't updated the OS X version in quite some time, and it's not open source so compiling newer versions isn't an option. That being said, it looks good in the graphics department, and the physics engine feels realistic.
The base install comes with just one track and one car type, so the idea is to download user-created tracks and cars which you can find links to on Racer's website (there's also a huge number of tracks and cars available here). They're generally high quality though I had to turn down the graphics settings to get good frame rates. On a low end machine like a Sawtooth forget about racing other cars. You can barely get usable frame rates racing alone. Obviously it's much better on the AlBook, and there's also an .ini file you can edit beyond the preferences presented in the GUI.
VDrift is about, you guessed it, drift racing. In many ways this is the best of the three. The graphics look good and framerates are higher than Racer. The physics engine feels very realistic, and you can also download and install new tracks and cars. The only negative was you can't collide with other cars. You just pass right through them (or they through you).
The ability to have car collisions came with the update just released, but it's Intel only. A developer in the forums said they'd try to build a universal binary but wasn't sure it was doable. Also if you download the previous version that supports PowerPC, the AlBook with an ATI 9700 Mobility renders smoke as solid white, no transparency, so it's not playable. The 2009-02-15 version, though, works great. Lower end users like on a Sawtooth might want to try version 2008-08-05 for better framerates.
Finally there's what may be the most addictive of them all, TORCS (The Open Racing Car Simulator). I don't know if the physics engine is totally realistic. It feels very frenetic and too fast at first. I've dealt with this by choosing older "historic" cars to race with (old sports cars from the 60's & 70's) which don't drive as fast and are easier to handle. That being said, this is the most action packed of the three. Some cars even deliberately bump you and try to take you out. The framerates are high, though the graphics aren't up to par with VDrift and Racer. It actually varies between tracks. Some are good, others look very 2002.
The latest OS X version on their website is 1.2.4, but Stephen Hudson has made his compile of 1.3.0 available here (UPDATED link here), so that's the version you want. It's a universal binary so it'll run on PowerPC. Unfortunately the latest version available to Windows and Linux users is 1.3.1 whose most significant changes are the addition of several cars and tracks, including the two best tracks from a graphics standpoint, "alpine-2" and "forza". However, 1.3.0 users can install these, too. You can download the 1.3.1 tracks separately here and install the new tracks in the TORCS app package by clicking "Show Package Contents" and placing the individual track folders in Torcs.app/Contents/Resources/tracks. Dirt tracks go in the "dirt" folder, road tracks go in the "road" folder, etc. Alpine-2 and forza are road tracks. I haven't tried adding cars with this method yet, but I suspect it would work, too.
With all three of these games you can use the mouse for steering. Only VDrift recognized my ten year old Macally iStick. There are no OS X drivers for the stick, so it's a crapshoot whether a game will recognize it. As far as maximizing framerates, toggle the view button so there's no hood visible (in TORCS) or at least put yourself inside the car (Racer), and limit the viewing distance to as little as you can tolerate.
Anyway, try all three. You're bound to get addicted to at least one, and then we can all enable each other's addiction and dig our claws into each other and drag each other down:)