[EStokely]

As for a manufacturer they are all about (I said about) equal
Things you need to consider/look for
1) will you be moving more than about 250 degrees? if that is a yes then you don't want a regular 1 turn.(they don't actually go 1 full turn) You want a multi turn Pot.(think of how older radios have a volume control, you spin for a while and then they hit a stop) we normally use 3 turn 10K pots for things that we need to track for about 1 full rotation (like an arm)
you would prefer a 100k but I never have found a 3 turn 100k Pot.

2) Make sure you use a linear pot, not an audio one. the audio stuff is logrithmic and will not track at all how you want.

If you can use a regular 1 turn then get a 100k.
You'll read the positions as an analog signal, 8 bit 0-255. the nice part of this over the Banner sensor idea is that the robot will 'know' where the arm is at power up. The Banners would not be able to do this.

Hope this helps.
Look at Mouser or Digikey for the multi turns. Radio shack or Fry's should have linear 1 turns