Simple trick I have been using with my sites that I didn't see mentioned here, even though its pretty obvious lol.

AboutUs.org is a PR6 and has a lot of authority.

Anyways, go to: http://www.aboutus.org/Do_Follow and read the instructions.

Basic information you need to add to your webesites page (can be easily done in 5 minutes):

- contact info on the left
- a unique description of the website (in your own words and that can't be found elsewhere on the Web) in the main Wiki section. (Tip: You can do much more than plain text here. See Wiki Editing Help for instructions.)
- a logo at the top left (this will become another link to your site)
- a short summary at the top where it says "click here to sum up this website"

I always get approved for my websites and all I do is add my email as contact information, upload a logo on the top left and add a article (400-500 words). Don't use a article that isn't unique though, they won't accept you, either pay $2 for an article or write it yourself.

This is a great and easy way to get a high PR contextual backlink.