A few possibilities you might want to consider would be a high-end P&S, a micro 4/3rds, or a Sony NEX.

A higher-end P&S camera (e.g., Canon G-series) gets rid of (most of) the shutter lag common in the cheaper P&S cameras. Image quality can be pretty decent as long as you have lots of light, but like other P&S cameras it deteriorates very quickly in lower light. These also typically cost close to as much as a low-end dSLR that will generally produce considerably higher quality pictures.

A micro-4/3rds is more like an SLR -- they use an electronic viewfinder, but still have interchangeable lenses. They're smaller/lighter than an SLR, but still rather on the largish side for a P&S. The sensor size (and low-light performance) is similar to an SLR.

The Sony NEX are slightly different from micro-4/3rds -- they have a slightly larger sensor, and different lens mount. Otherwise, they have roughly the same tradeoffs; bigger than most P&S, but smaller than an SLR. Image quality is roughly on a par with an SLR -- better than many older SLRs, but not as good as a current higher-end SLR.

None of these addresses focusing speed though. SLRs using phase detection focusing, which is a large part of what lets them focus so fast. P&S cameras use contrast detection focusing which is almost unavoidably slower.

If you want the fast focusing of an SLR, about the only choice is an SLR. For small size/light weight with excellent quality, a Pentax would be a strong possibility.