For those looking for information of PageRank and how it works, tune into Darren Franks' description. He explains that too many outbound links on a Web site can deplete a site's own PageRank, but
there are ways to link to relevant sites without reducing the importance of your own.
Read the whole story at MoreVisibilty »
Hold on - Didn't Matt Cutts explain that adding a nofollow attribute to a link DOESN'T help you retain PR (you still 'lose' link juice but it's not passed on to the external URL).
I don't think this article explains outbound links well at all. My understanding is that this quote is incorrect:
"...[PR loss} can be completely avoided with the nofollow attribute. A few years ago, Google put into action the nofollow attribute so webmasters could link to other websites without losing their own “link juice”. This is useful if a webmaster wants to provide links to other quality websites for their users and not lose their own PageRank status. "
Thanks for your comment, Aidan.
From Google themselves concerning links with nofollow:
In general, we don't follow them. This means that Google does not transfer PageRank or anchor text across these links. Essentially, using nofollow causes us to drop the target links from our overall graph of the web.