What kind of exercise bike should I buy?

[Wynton]

Just noticed this thread. I'd like to hear more opinions whether recumbent bikes provide good cardio or not.

Also, I have somewhat cranky knees, which forced me to give up jogging years ago. For the same reason, I avoided stationary bikes. But now I really need to get more cardio in my life.

Are there any stationary bikes that are known to cause less knee strain?

[astroglide]

i would expect to find really cheap ones on craigslist, in classified ads, etc.