We have our own pages at various social websites:
LMMS Sharing Platform
We have a central platform to upload your content made with LMMS. See Share your songs! for details.
Forums for our users are available at http://sourceforge.net/apps/phpbb/lmms/. You'll need a SourceForge account in order to post messages.
List for discussions concerning development, new features, releases etc.
All users who are not interested in actual development but LMMS itself can subscribe to
If have problems with the mailing list (e.g. subscribing) or want to have other mailing lists, contact us!
Since LMMS has grown continuously, it's no longer a one-man-project and also your help is needed! There're many important things to be done and it's not just programming! You can write documentations (mainly in the Wiki), add or improve translations, help improving usability or simply test and report bugs.
If you're interested in helping us, join our IRC channel (see above) or write a mail to the lmms-devel> mailing list, tell us what you intend to do and wait for reactions.
More details on what can be done are available at the Roadmap/TODO-list in Wiki.