After the today's workshop, I got these three tips for a MOSS developer:
SPDisposeCheck utility for alloc/dealloc SP objects (SPWeb, SPSite etc.) check up
ActiveDirectory wrapper from .NET 3.5 - AccountManagement namespace - easier AD
Master pages override - when in need to re-set dynamically the master page to a "non default" one, David Wise writes back in 2007 the code for it, using PreInit event of the Page in a httpModule.