It could, of course, enable you to find new tweet discussions to join, which could expand your tweeting activity, but with Communities currently being either 'invite-only' or 'open to all', that means that you either need to know somebody already in an interest area to gain access (and community discovery is not overly intuitive), while 'open to all' groups are generally filled with spam - which even the invited groups are as well, to a degree, due to flaws in the joining process (each new member can invite five of their own connections).
[
add
]
[
|
|
...
]