Panasonic GH1

I used to discredit the GH1 because it had a very weak recording codec which resulted in very bad aliasing and moire. Some very clever people have since figured out how to hack this little camera which now makes it a real contender. 

I've only ever laid my hands on a GH1 a couple of times so I can't really speak for it too much. It does however have some real plus points going for it. First off is the ability to hack it. If your techy minded enough and have the guts to do it (although it seems reasonably safe) then you can turn this into a very powerful camera. Next up is the flip out screen, a really useful feature that I wish my Canons had. Lastly it's cheap and is also smallest (and therefore least conspicuous) of all the models out there.

Downsides? Slightly smaller sensor means that it doesn't perform quite as well in low light as some. Also lens choice seems more limited than with a Canon or a Nikon. 

If your happy to hack your brand new camera then this should be a real consideration no matter what your budget. If not then your probably better off going for a different model.

UPDATE: Panasonic have patched the hack, so if you want to go down this route then you have to buy a camera with an older version of the firmware installed.