For anyone working with Microsoft technologies there is a huge range of events available via the Microsoft website. There's a format to suit everyone - in-person events, on demand and live webcasts and virtual labs.
Some of the skills featured are ones that charities are desperately looking for help with. For example, we've some opportunities needing Sharepoint skills, lots of charities are concerned about the effect of Vista on their work and many would appreciate advice on the licensing issues involved when purchasing software.
Although we don't encourage volunteers to offer skills that they don't have there's nothing wrong with honing new skills by volunteering. Often the voluntary sector environment can be less pressured than at work and you may have more time to read up on new techniques and experiment with them. But please don't over-stretch yourself on mission-critical applications and do let the charity know if you're using them as a learning environment.
