No good on the Canon EF lenses due to the electronic control of the lens, however there are adapters to use Canon FD lenses, which are still relatively inexpensive compared to similar EF lenses.
These days FD and FL GOOD lenses are not the good deals they once where. Some border on the ridiculous range.
I heard if you drop the aperture on an EOS body and remove the lens right then, the aperture remains where set. It will allow for smaller aps, but still can't control them.
I have an EOS adpator to m4/3rds adaptor (RJ/jinfinance on ebay). I bought it primarily to use my 45 TS and Lensbaby but have tried a number of lenses, for fun, on the G1. To be truthful, they really would be awfully unbalanced on the GF1 (which I have also).
To change aperture, you set it on the EOS body, hold down the DOF preview button as you dismount (must not turn off camera body). That's not really a very effective use of a small cam, is it??--unless you are content to set the aperture and live with it for the day (or until you get together with your EOS body again). You can check a number of EF mount lenses on an m4/3rds body here http://www.pbase.com/picnic/eos_lenses Personally I don't plan to shoot with any of my EFs on the GF1,
I do have 5 FD lenses--KEH still has some quite good deals and their ratings are on the low side so you can buy a bargain or good and get a lovely lens with perhaps some cosmetic dings. I much prefer to shoot with the FDs---they have manual iris control, are smaller and lighter (generally) and suit the cameras better.
