Wikipedia's list of active Solar System Probes. There are a bunch, and just perusing it I wasn't getting a very good picture, so I chopped and hacked and stuffed it into a spreadsheet, and thence I got this graph. It's not perfect, but it does give you an overview of what's going on.
The numbers across the bottom are the year. The right end of the blue bars shows when the probe was launched. The end of the red bar shows when it arrived at it's destination. The difference is the length of time in transit. Some are very short. One probe made it to Mars in six months. Some of them, like Cassini, take a very long time to reach their target. Rosetta was the ESA probe sent to chase down that comet. Messenger went to Mercury. New Horizons is heading for Pluto.
3 hours ago