StumbleUpon, an SF-based startup which makes browsing tools and sharing of sites easier, has raised an angel round, and launche in beta. The angel round was above $1 million (exact figure not known)...investors include Ron Conway, Mitch Kapor, Stanford professor and early Google advisor Rajeev Motwani, Ram Shriram and many more.
SU is a Firefox and IE extension that lets you “stumble upon” (aka discover) websites/links , and then rate them. Based on that, it also delivers personalized content. More details in the release here.