Here is what your URL will look like: http://www.academia.edu/yourusername

The best feature of this is that you will have your keywords as anchor text in the sidebar of your profile. The sidebar links are nofollow however. All of the link in your status update and on the website itself are dofollow.

This works best if you put some time into creating your profile with some interesting info. Add some interest, some genuine looking status updates etc. I also recommend linking to your profile as much as possible, sending some backlinks to it will get it seen by Google quicker.

Here is a link to a profile I created.