Stumblers
Stumblers blogs are interesting places themselves. Every time you "discover" a new site, comment on someones site, discovery, or write in your journal, you are creating your own stumble blog entry. Most of mine early on were random things I came across. My later stumble blog posts were directed to driving traffic to specific places. Many stumblers create fantastic visual blogs. There are channels on SU so you can stumble only pictures, video, music, or people. (stumblers) By stumbling only stumblers with similar interest you can find some great information about almost anything you want. Take the SU tutorial for a full discovery of the site.
Final Word
SU is entertaining, informative, addictive, and you can be either very productive or waste an incredible amount of time playing around. Learn to use it in a way that is most appropriate for your situation. Ask other stumblers for help or advise. There is even a guy on-line named Mr. Helpful. He is happy to give you advice on almost anything. Play around for a while and if you come up with more useful uses for SU let know.

Rob,
Thanks for the post! I "stumble" around the internet alot, especially early in the morning. My wife and I have a one-year-old and my stumble time has been severely hampered. I have learned alot by stumbling over the years...
You know, I have an account at Stumbleupon, but never got there. Actually, I have accounts on most social networks and don't use most of them. I guess I should be more involved, I just have a hard time finding the time for all of them.
Thanks for the post Rob I have an account with SU but have yet to find away to incorporate it into my business. Your post has encouraged me to take another look at a website I previously considered another waste of time on the internet.
I didnt think it could be useful for real estate people.