The second (even bigger) event will be the first MeeGo code drop (a technical preview release for developers), also known as "Day One", which is scheduled for Wednesday (search for March 31), and also a TSG meeting later that day.
Last, but not least, while not really announced, the Nokia N900 PR1.2 firmware release, probably the most important one so far (as it brings all-important official Qt4.6 compatibility) could easily happen this week. The early access PR1.2 SDK has been released a week ago, and the autobuilders on maemo.org have already been transitioned to PR1.2, so the firmware itself can't be far.
The MeeGo release is certainly the most important of all these events, so prep your hacking skills, you're going to be able to put them to good use in just a few days !
EDIT: As pointed out below, this week will also see the election of the Maemo Community Council, which while not strictly a Nokia activity, still plays an important role in the Maemo world. If you are a Maemo community member and have received a voting token, take a gander at the candidate list and their programs and make sure the candidates who you think are best take the seats!