That depends on what you want to do.
Cbox is a good place to just chat with other members.
The
Bored Games section contains forums games.
Iwaku also has a nice
Content sub-forum containing challenges, showcases, and much more.
Of course, Iwaku is a roleplaying forum! Therefore joining or creating a roleplay might be a good thing to do next.
You can view up and coming group roleplays in the
Interest Check sub-forum.
You can find already existing group roleplays which are recruiting in the
Roleplay Advertising sub-forum.
You could create your own thread in the
Seeking Group Invites section. This way people can read what you are or are not looking for and offer up their own roleplays if they fit.
Or if groups aren't your thing you could browse the threads in the
One on One section. (Or create your own thread!)