What brand of cranks would you all suggest I buy for a first fixie? It's gonna be kind of a beater. I'm also wondering what lengths cranks come in generally. Also, I'm a tall kid, converting a frame that's too small, so wouldn't shorter crank arms just make the bike fit worse and worse?

I'll preface this by saying that I'm an amateur at this anatomical reasoning thing so feel free to argue.
Well, about fit, the crank length sorta follows some general suggestion sort of rules.
ie. A track bike will have a higher BB and allow longer cranks in a situation where shorter cranks would be ideal on a road conversion with a low BB. Longer cranks are generally cool for people with longer-than-average legs because the larger diameter leg turn has a more proportional knee movement. Shorter cranks are easier to spin but have less mechanical advantage, which, I would imagine, would be pretty nice to have on a fixed gear. So I would advocate countering an increase in crank length with a spinnier gear, as a balancing point and to make more of the leverage flex to reside in the rigid parts(crankarms) rather than the comparatively stretchy ones(chain, rear cog), as to provide a very(very) incrimental boost in efficiency. I admit the advantage gained by larger cranks and low gearing vs. smaller cranks and higher gearing is mostly negligent, but that argument is mostly academic anyway.
So, do you have a track bike with a higher BB or a road conversion with a lower BB?

edit: bad grammar make me cry

that would be a peugeot road frame. so... lower BB.
~Oni

I say cheap is good. Bulletproof or Dotek offer inexpensive, light alloy BMX arms in from about 140mm to about 170mm. I think they both use 110mm BCD chainrings. I think they sell for about $30 a set.

For a lower BB I'd go with 160-165 and learn to time your pedaling while cornering. 160s feel okay for me and I'm 6'5".

why not make your own cranks

or pull your own crank

Now you are just being cynical..

Phil

what the hell? "Make your own" cranks?

Chicken bones and cat gut. Works every time. Just don't forget the loctite.

1. Check LBS(s) for junk bins for cheap cranks. This is for a beater.
2. Get a set of Shiitmano Sora cranks from harriscyclery
3. eBay
4. Make your own (a few things to get the creative juices flowing):

I'm assuming you ride a bike like this:

eBay. Don't get cranks designed for triple chainrings, they don't line up well. Shimano 105s are pretty nice.

I have cheap 175mm mt. bike cranks on my beater, they suck. They flex and the pedals scrape on tight turns. 165s on my track bike; I'm 6' and never had a problem with this length.