Yahoo! del.icio.us
Yahoo! has made some prescient purchases lately. Adding Flickr to the fold was neat, but questionable given Yahoo!'s own photo-sharing service. But their acquisition of del.icio.us brings a lot of utility to the table that I don't think Yahoo!'s had before. As with all these acquisitions, I hope the service remains relatively unchanged from its core functionality, and uncluttered with roadblocks that might stand in the way of using del.icio.us the way many of us have become accustomed.
I've been using del.icio.us since Ross pointed it out, and I'll admit I've taken it for granted. I use it as my linkblog. Congrats to Joshua and the rest of the team for persevering and making the service attractive and functional.