need an inexpensive heart rate moniter

I have the bottom of the line Polar (don't know the name, sorry). It was about $35 dollars. It stays in place, and the readings make sense.

Polar FS2 was about $35 from my local running store on sale.

Check out www.performancebike.com.

They are always running a sale. I just picked up a cheap Sports Instruments HRm for my wife - it cost nme about $44.

If you look at the "returned" section of nashbar or it might be performance sport, they have great prices there too. 

Polar FS2.  Inexpensive and easy to use.  It is very basic though so be sure it has the features you are looking for before you buy.

I just bought that same HRM for myself. Cheap as all hell. Sports Instrumencts ECG3.

I'll piggy back the polar HR monitor... reliable as hell, they were the first in their industry. I think the A series is cheap? 39 bucks free shipping.

http://www.polar-usa.us/google.html

good luck

If you think that you are going to use the HRM beyond your spin class, you might look at spending just a little more money and getting something like the Polar S120. You can find it for $65-70 online. It has some additional features like lap splits and average heart rate for those splits. Comes in handy when running.