Figure $150k+ per car per race to have the full car, aka not worthwhile.

A much better option would be running commercials, say on Adult Swim, or on something like G4 TV.  Each spot could be done for a few K depending on the time it runs and some other factors if you wanted to hit mainstream.

Billboards can be done for ~$1.5k per month depending on the area too.

Thanks!  As for overclocking, any idea on how much that would bump it up from the 800 W level?

CPU: AMD Sempron 140
CASE: open (n/a)
HDD: 16 GB SSD
3x ATI 6970's (slight overclock)

Do you think I can reliably run 3 of these ATI's on a 1,000 Watt PSU?

Using Newegg's Power Supply Calculator, it says I would need 1168 Watts.  Hoping to get by with less, if possible.

That's a myopenpc case right?  How is your bottom card mounted?  I notice it's sitting higher than the top card.

I enjoy Ruby/Perl/Linux (coding) and would love to contribute to some interesting bitcoin related projects.

So you're doing about 1 Megahash per second, which is very, very low.  It would take a long time to generate a block at your current rate.  I would suggest that you join a bitcoin pool, or build a mining rig, or both.

CPU : Doesn't matter, get the cheapest CPU possible for your motherboard.  The AMD Sempron 140 is recommended a lot.  A lot of people downclock their CPU to conserve power.
RAM : 1 GB is enough for Linux, for Windows 2 GB is the way to go.  Get the least amount of sticks as possible.
HDD : Go cheap and small here.  If you can get a cheap 30 GB SDD, do it since it's more power efficient.
OS : I prefer Ubuntu if you wanted to go Linux as a lot of tutorials and drivers are geared for this Linux distro.

I'll let someone more experienced address the PSU/motherboard options.

People have been saying this for months now.  Yes, it's getting harder and harder to generate blocks of bitcoins, but being that bitcoins are by nature deflationary, the value should be going up as well. 

I'd like to contribute to the frontend pushpool code (I know Ruby/Perl and some PHP), there's a thread here http://forum.bitcoin.org/index.php?topic=8760.120 that I'd like to reply to.

Thanks in advance!