I would add bloglines to the list of useful sites. If you're looking to keep up to date on what other blogs are doing and the latest news (i.e. keep up on the latest news in your interest area), bloglines is the best reader to use.
http://www.digg.com/ http://del.icio.us/ http://www.furl.net/ - kind of tagging site or maybe web2 style search
feedburner.com - so you get stats for your RSS feeds reddit.com - social bookmarking botd.com - blog of the day feedsubmitter.com - get your feed found