Technology user groups benefit both a technology (with the companies behind it) and its users. Java user groups around the world played a big role in the adoption and advance of the Java language and platform. Even now that Java is in its old age (or on its deathbed, depending on who you talk to), JUGs are actively promoting educational and community-building initiatives.
The Groovy community is benefiting similarly from a growing number of user groups. There are currently a few dozen groups around the world, and more are forming every day.
Now there is a website that can help you find a group in your area or help you get one started. G2Groups.net has a list of active Groovy user groups, with links to their sites. If you can't find one in your area, you can propose one. The site will post a link to your proposal on Twitter; you can retweet this to help get the word out. Then when others are interested in your idea, you'll get emailed about it, and you're off and running!
Once you get a few likeminded (and by "likeminded," I of course mean "brilliant") people together and get a group started, send me a note, and I'll invite you to the Groovy User Group Leaders list on Google Groups. This list is a great way to get support and ideas from other Groovy/Grails/Griffon/Gaelyk/Gradle/Getc. group leaders.
I've always said that the best feature of Groovy and Grails is the community. User groups are a big part of that. So if you're not already involved in a G2Group, get plugged in. You'll be glad you did.