I’m using a combo of Twitter @witchlinks and Tumblr.
I was using just del.icio.us, but I started using it more for what it was designed for, bookmarks. I use it for research, tools, etc.
@witchlinks at Twitter is a live feed of all my shared spaces. It updates with a service called twitterfeed my Flickr, Google Reader Shared, del.icio.us, YouTube, my Blog Oklahoma Network, and a few other social and shared spaces.
I use Tumblr for quick notes, interesting videos, and as a way to test out Tumblr itself.