Joel Ainsworth has a great list of SIX reasons you should join a Missional Community. He gets into a lot more detail over on his blog with some good Scriptural references.
But it’s a great list:
1. God Desires for You to Be on Mission
2. God Desires for You to Have Community
3. There’s a Mission that Matches Your Passion
4. For Every Man, Woman, and Child
5. Church Doesn’t Reach Lost People
6. Everybody’s Doing It
In particular, it’s awesome that “everybody” is doing it in his environment. I find this inspirational.