Fair enough... I guess I assumed you knew what you were looking for. If your question really is, "what are the general market offerings for hosted blog platforms"... then it seems to me your asking a basic market research question. You ought to be able to find some good information from the two resources I mentioned.
Here's what I'd do if I were you:
1) Research the target market you're trying to service. What do they care about? Are there competitors out there already servicing the market, what features do they have? What features are the missing? etc.
2) Research the generic hosted blogging platforms... like blogger.com, livejournal, (uh) wordpress.com, etc. What features do they offer?
Based on the list of features you come up with, I'd start searching the wordpress "extend" resources, and google.
For example:
* Spam Protection
* Captcha (?)
* Avatars/Profile Pictures
* Video plugins
etc etc.
I dunno, I think the list is pretty obvious... and if you go to the two sites I mentioned I'm sure you'll get some good ideas.
I don't know how to be more helpful then that.