Besides the obvious answer of forums, I also use my computer for some gaming, writing, browsing the internet, watching TV/movies, listening to music, and just general "chores" (for lack of a better word) like paying bills, checking email, and making sure I haven't overspent on my accounts.
I make use of my computer in looking for new cake designs. You know that there is a need to keep improving every day, and that is what I use my computer to do.
Like everyone else, I use my computer for a little bit of everything. Forums are definitely what I access on it most of all, but I'll also use it to watch Netflix, YouTube, etc.
Besides my forum, I use my computer for blogging. I purchased my laptop so that I wouldn't be on the desktop all the time and drive my husband nuts. So I use my laptop and that allows me to stay off the desktop.