Answering the second part of the question...
The other alternatives to Obsidian Portal that I know of are Epic Words and My DnD Game.
Epic Words seems to have more features than Obsidian Portal (eg. it actually has versioning on the wiki pages, character blogs, a loot tracker, XP tracker, free campaign forum, session scheduler, etc). By default, you don't get any file storage, but if you upgrade your account for $12/year, then you can get 1GB of storage).
The downside is that the interface is...not as pretty as Obsidian Portal's, which may or may not matter to you.
I haven't had a close look at mydndgame so can't really give much more info on that, unfortunately, though all three websites are free to sign up to if you want to have a play around.