earl_brutus, e-510 is an SLR, although they are pretty small for an SLR they’re still quite a bit bigger than compact systems. However, it’s worth noting that I picked up an e-420 SLR, which is apparently the smallest ever made, in sparkling new condition for £120 including lens. No image stabilisation, limited ISO range, and not the fastest continuous shooting speed but a tiny real SLR for peanuts!
daftvader – 4/3 is the lens fitting system used by Olympus. Micro 4/3 is a different (but related) smaller system used on compact system cameras, and is used by many manufacturers. Most manufacturers have their own lens fit system, but micro 4/3 is supposed to be an open standard.