I've done a lot of research on the old Nikon glass for use on my 5D Mk III. Nikon ruled the professional range in the 80's, and has excellent support on Canon mounts with adapters. Beware that some have glass too far back and may get in the way of the mirror. I mostly wanted something that I could use as a good reverse lens for high magnification macro shots, so I got a 24mm f/2 AIS lens for ~$200. It's a decent lens, and will get nice shots when I have time to manually focus the lens. The bokeh is very different, sometimes distractingly so. This was one of my first sample shots I took of my daughter at very close range:
Tea Time by
yorgasor, on Flickr
Here is a list of other Nikon primes I'd like to eventually get. It's a solid list, and I tried to pick the best ones from each focal range. Some of them are still pricey, enough so that I'm sure I'll end up getting the Canon 135mm L lens, which has a very nice autofocus, and only a couple hundred $$ more, and would be much more useful. I didn't find any notes in my research that any of these were incompatible with Canon, so do some due diligence and make sure before you make a purchase.
nikon manuals lenses keh.com
300mm f/4.5 ed-if ais $300-400
135mm f/2 AIS $650
35mm f/1.4 ais $500
85mm f/1.4 AIS $650
28mm f/2 ais $200
50mm f/1.8 ais $100
The 300mm lens is the most intriguing for me, as my current lens collection maxes out at 200mm. If I were you, I'd probably only get the 50mm and maybe the 28mm nikon lenses, and maybe the 300mm if you're looking for a good way to get reach. The other ones are expensive enough to make it not worth the hassle of vintage / non-autofocus.