Hello, I am building a new computer and I need a good mice for around $20, and I was just wondering what your opinions were on some mice.

I have wireless and battery free mouse, which consumes power through it's mousepad, which is connected to usb.
Cool thing. Wire does not interrupt movements and you don't need to chnge batteries - everything I ever need in mice.

@EF could you post a name or a link to this mouse. Sounds interesting.

How much was it? Cause it sounds expensive.

Nah, it's rather cheap: about 12 dollars (tho I don't live in USA)
Mine is A4 Tech NB-30

Here's full set of these mice
http://www.a4tech.com/products.asp?cid=142&scid=122

Also, it never disconnects, goes to sleep or anything - you don't have to wake it up. I hated this in my ordinary wireless mouse to.

Does it need feeding, if so what does it eat?

http://www.amazon.com/Logitech-Performance-Optical-Gaming-Mouse/dp/B0001YGIB0

Will never fail you. Going on 2 years and this thing still works like the day I bought it.

I have a simple logitech mouse that is going strong after ,I believe, 3 years.