Did someone call?
You have lots of options with the Canon EOS system
Namely:
M42 screw mount lenses
Pentax K mount lenses
Olympus OM mount lenses
Contax / Yashica mount lenses
Nikon mount lenses
Exakta mount lenses
Leica R lenses
Prakticar PB mount lenses - these won't focus to infinity though
Tamron Adaptall / SP lenses
Old T-mount lenses
There are loads of great M42 lenses out there. Try a Carl Zeiss Jena 135/3.5 sonnar lens...it renders beautifully. Or a Carl Zeiss Jena Flektogon 35/2.4 or 35/2.8 (but these are getting expensive). The Carl Zeiss Jena Pancolar 50/1.8 is reasonably fast.
M42 Asahi Super Takumars are also great and generally better built than the East German Carl Zeiss Jena series. The 55/1.8 is always very cheap whilst the 50/1.4 is rising in price. There is a whole series of wider and longer prime lenses available too.
If you want something a little cheaper, try a Russian clone of the Carl Zeiss Jena optics e.g. Jupiter 11A and 37A are clones of the CZJ 135/3.5 and can be had for around £20. The Helios 44 already mentioned is a 58/2 CZJ Biotar clone and can be had for £10.
The Pentax K series lenses are also great value...I picked up a Pentax-M 50/1.4 for £35.00.
Olympus Zuiko lenses are pretty much all brilliant! The 50/1.8 is starting to increase in value but can still be had for £20.00 or so. The 50/1.4 is less common but can be found for about £50.
The Contax Carl Zeiss lenses are STUNNING! Grab any you can!!

The Planar 50/1.4 is gorgeous with incredible "pop" whilst the 50/1.7 isn't far behind. The Distagon 28/2.8 is a cracker too, also with great pop. There exists a Hollywood 28/2 version but it's pricey! The 85/2.8 Sonnar is sharp from wide open, but the Planar 85/1.4 would be more useful for shooting indoor music videos. The Yashica ML series are also very well made, and whilst not as good as the Carl Zeiss lenses, are still extremely good performers.
Nikon lenses are plentiful and of great quality. The pre-ai lenses are less valuable as Nikon shooters can't meter with them / find they break their camera's metering prong, but they work fine and meter on Canon DSLRs.
And as for Leica...if you've got the cash...
Adapters can be found on ebay for very little. Sellers like big_is and jinfinance have all provided me with decent adapters over the past couple of years
