Create a BuddyPress-enhanced WordPress theme and submit it to the WordPress Theme repository.
Create a BuddyPress-compatible plugin or bridge an existing WordPress plugin to work in BuddyPress and submit it to the WordPress Plugin repository.
Help others at https://buddypress.org/support/topics/
Web-based IRC client: http://java.freenode.net/
BuddyPress dev chats generally happen every other Wednesday at 19:00 UTC in #buddypress-dev. To find out what time 19:00 UTC is in your country, look here.
The BuddyPress Development Blog is at bpdevel.wordpress.com.