A former boss of mine instituted the 'Monday morning tech session'. Every week, one person from the team would talk about something technical. It might be something they were passionate about, something they recently had some training on, some project that they've finished that colleagues will end up supporting, a tool that everyone used that they knew more about (vi tips anyone?). Sometimes we'd get a 'guest speaker' in - perhaps a rep from a vendor, perhaps even a customer to talk about what they used our system for.

Having it every week is (I believe) a key to its success - if people have to wonder "are we doing it this week?" then it will fizzle out (indeed it has more than once). Keeping it informal and short (max of a hour) is also important. Scheduling it first thing in the morning was a good idea because it meant people were less likely to get sucked into something else - unfortunately if everyone doesn't start at about the same time it might not work so well. If the company were to provide coffee and donuts that might help :-)