Singlespeed & Fixed Gear - help me with a new crankset

i need to get a new crank for my fixie, but i don't really know what to look for. All i really know is that i want a chain ring with 42 teeth, and probably 170 mm.
so far i've found THIS (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=56195&item=7156523488&rd=1&ssPageName=WDVW) and THIS (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=56195&item=7156515529&rd=1&ssPageName=WDVW). Do either of those look any better, and can i really expect to get a decent crankset for 20 or 30 bucks? And also, what does BCD mean?

Eww, biopace, I know Sheldon likes 'em but I'd still be scared to run a biopace ring.

As for your question, you could spend a bit extra and get an IRO crankset. They're very nice, and go for about $80 which isn't bad for a brand new crankset. Although, they only come with a 46T chainring. BCD refers to the spacing between the holes on the chainring, Bolt Circle Diameter.

Is there a certain BCD i should look for?

144 is nice because you can run track chainrings.
you can also pick up road chainrings in 110 and 130 for very cheap, they are very common.

it bothers me that on the biopace chainrings, the logo is not opposite the crankarm. that would drive me nuts

Harris has the Sugino RD cranks for $79, good stuff for the money. I just picked up a set for my ladie's new fixie project.

http://harriscyclery.net/site/itemdetails.cfm?ID=1467

I'd reccomend a crank with a 110 BCD. It is super versitile, because you can run MTB rings, BMX rings, and road compact rings. This means cheap and plentiful chainrings.

the sr cranks are nice

the sr cranks are nice
Totally. Buy those.

chucks bikes has a set of sugino AC130 170mm cranks for friggin 15 bucks. They're nice (crazy nice for 15 bucks), I just got them. Sans chain ring though, if you can find one and have the short stack chainring bolts to boot, you've got yourself a nice crank set for cheap.

i have to say that my sugino 75's were completely worth the money. one of those 'you get what you pay for' dealies. honestly, made my ride 100% better than the bulletproof ones I had before, or the deore (ouch) ones before that.

You are right on the money so far dude. Those Ultegra cranks would be perfect(although the Biopace kinda scares me, just fear of the unknown though). I just picked up a set of 600's for a friends buiid off of eBay for $40 last week. I like to use Shimano because I find that most Shimano cranks mate very well with a 107mm UN-53 BB to get the chainline in pretty tight. It takes the guesswork out of the whole chainline process. Keep shooting for a set like those and you will get a nice crankset for cheap.

so what exactl is biospace?

http://www.sheldonbrown.com/biopace.html

It's supposed to look like this:

http://www.sudibe.de/fotos/technik/biopace38.jpg