There are a number of micro four thirds cameras on the market today. These cameras all have interchangeable lenses and cost about the same as some of the DSLRs on the market. The difference is that the DSLR has a mirror inside whereas the micro four thirds cams don't.
Sony is rumored to be getting ready to enter the micro four thirds market with a new Alpha camera supporting the format. The new camera is said to have a snap on lens mount system that needs no twisting for faster lens changes.
Along with the camera three lenses are rumored. The lenses include a 16mm f/2.8 lens, an 18-55mm f/3.5-5.6 lens, and an 18-200mm zoom lens is rumored as well. The launch date for the camera is supposed to be May 11.