Welcome to the forums.
We've got some cool places to go, I personally favor the Off-Topic forum and it's "Forum Games" subforum. Though I would warn you of the memes and shitposts there, it can be pretty fun. Forum Games is where the fun is at, Off-Topic is where the drama's at. If you're not into the drama, skip past OT into FG. They also have a Surveys subforum, so you can answer some questions there. If you're creative or are interested in the arts, check out the Music Hall and the Art forums. The General Discussion forum is self-explanatory, and judging by your use of this forum, you're familiar with Introductions.
Of course, there are a lot more, but I'm more familiar around the category "Other". There are forums regarding gameplay, development, and beatmapping as well, so if those interest you, check them out as well. Feel free to explore.
That's all I've got, so we'll see you around!