As a result of a long vacation over the Christmas break, I was able to spend a lot of time exploring StumbleUpon. Although I feel like I might be a little bit late to the party with this one, I think that it is a very clever bit of design and I'm looking forward to playing with it a bit more (despite Mark Evans finding it only "quasi-interesting"). I also started using Twitter (add me and I'll add you back) and am not nearly as enthusiastic about it. However, it seems like many people are finding a great deal of value in it and I think I just haven't given it a good enough chance. Ditto for Del.icio.us.
Because of this, I have decided to devote some time to really learning about each of these sites/services in the next few weeks.
I'll be reporting back later with my thoughts and hopefully have a good idea of how Twitter, StumbleUpon and Del.icio.us can be of value.
I know that there are a lot of veterans of these tools out there and if you have any tips or suggestions (or even other sites tools I should be checking out) please let me know!