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.

Length	Aperture	Weight	Retail	Rebated
20	f/2.8	405g	$420	$375
28	f/1.8	310g	$400	$355
50	f/1.4	290g	$315	$270
85	f/1.8	425g	$340	$295
100	f/2.0	460g	$390	$345
135	f/2.0L	750g	$890	$785
200	f/2.8L	765g	$660	$585
300	f/4L	1190g	$1150	$1015
400	f/5.6L	1250g	$1100	$980

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.