Here are some important links to take a look at when getting started with MonoGame:
MonoGame.Net – official project home
Github Repo – MonoGame’s home on Github
XNA Creators Club – MonoGame tries to be faithful to the XNA API, so XNA resources are a good start
XNA Framework 4.0 documentation – From MSDN
MonoGame Samples – A blog post describing the updated MonoGame samples