We use a biometric at my day job. Its an APC Biopod. We use it in conjunction with Softex's Omnipass software 2.0. Its an older version but its much more stable than their newer releases and a lot easier to work with. We have an account setup with WebPunch by Time Management Solutions. We just link the Biometric to the Web Punch login. It works great for us with about 40+ employees. Been using it for yrs to keep employee's from doing the buddy punch!
Biopod - $6 refurbished units off Amazon
Omnipass 2.0 - Free (non supported xp version)
Web Punch - $2.50 per user for 3 months
If you're at all computer savey, experiment a little with what you can find. It dont have to be perfect it just has to work.