First of all congratulations, thank you, and welcome to the fold! If you are reading this you've recently been voted in as committer on an Apache Maven project and there are a few things that need to be sorted out before you can participate fully.
The first thing to get out of the way is sending in your contributor's license agreement (CLA). You can't participate at Apache until we have received your signed CLA, so go to the Apache website, print out the CLA, sign it, and send it in ASAP.
Once you've dealt with your CLA, there are a some documents that pertain to Apache as a whole you should read:
Here are the documents that pertain to Maven specifically:
If you have any questions just ask! We're here to help, and looking forward to working with you!
The Maven Team!