Canon has a yearly amazing rebate program; if you buy three qualifying items you get a 10-30% rebate on all of them. Rebates cover many things (including camera bodies), but you have to buy things by January 15. Here's a list of all the prime lenses that are covered by the program. Prices listed are the cheapest at Amazon, rebate is the maximum 3x rebate.
All lenses have ring USM autofocus except the 50 which is micro USM. The 300mm is also image stabilized. More data on the Canon lens chart PDF.