As for specific scanners you can buy:
The top of the line scanners are, hands down: Nikon Coolpix scanners.
They have all been discontinued as of late so fleabay, Craigslist, or refurbs are your best bet there. They are "dedicated" scanners, meaning: they ONLY scan film and nothing else. This is why they produce better image quality.
They also cost alot of money.

The middle of the road scanners after most dedicated scanners are:
Epson Perfection or Epson Expression scanners
They produce the best quality per price ratio.
The Epson V300, V500, V700, V750, 4490, 4990 are all great models.

The Canoscan 8800f is also good and is worthy of consideration

Dont get anything that you can not find information on. A POS scanner for $20 will give you terrible scans and will be a pain in the ass to work with.