I've been involved in the OpenstreetMap project since early October 2007. I think it's a creative project, and I thought I'd contribute with some mapdata myself! Besides, it's always good exercise to go for a mapping run, or just head out an hour or so on your bike. For mapping, I use a GlobalSat DG-100 datalogger, with an external antenna to increase accuracy. This equipment is ideal if you want a non-intrusive logger, which fits easily into your pocket and it can handle a beating. It also has a very large memory, capable of storing 16 hours (assuming you bring back-up batteries :P).
Currently, I focus all my mapping efforts to Lund (small-to-mid-size town in southern sweden), where I mainly try to cover as much of the inner city as possible (which happens to be where I live).
If you like to contribute to Lund, don't hesitate to contact me and we can work together!