If you like to immerse yourself in a character and spin improvisational writing riffs in real-time, you might like MUSHes. I run a few at
www.jointhesaga.com and there are many others out there.
Unlike the most popular graphical online roleplaying games out there, MUSHes and their text-based kin don't require top of the line computers and graphic cards to get in the door. All you need is an Internet connection, some easily obtainable (and free) client software, and a good imagination!
Even if you don't find what you like at my site, perhaps you'll have more luck checking out places like
www.topmudsites.com and
www.mudconnect.com to find real-time roleplaying/improvisational storytelling environments that are more to your liking!