If all outgoing links related your site and has a unique content, they increase your ranking via nofollow tag. According to Google:
Not all paid links violate our guidelines. Buying and selling links is a normal part of the economy of the web when done for advertising purposes, and not for manipulation of search results. Links purchased for advertising should be designated as such. This can be done in several ways, such as:
- Adding a rel=”nofollow” attribute to the tag
- Redirecting the links to an intermediate page that is blocked from search engines with a robots.txt file
http://www.google.com/support/webmasters/bin/answer.py?answer=66736