Everyone else is listing them. Here are mine:
NetVibes. My home page, my bookmarks, my RSS feeds, my ToDo list, my calendar, my Weather, my GMail. All on one page.
WordPress. You’re looking at it. Couldn’t live without it.
Flickr. Can’t go a day without checking my comments, my friend’s photos, my groups’ postings.
GMail. I actually don’t use it that much, but nice to have. I usually use my GMail address when I have to give an address to sign up for something. That way it gets all the spam and filters it rather nicely. Integrates nicely with NetVibes too.
GCal. Decent calendar, accessible from anywhere. Integrates with NetVibes.
Brightcove/Google Video/YouTube. OK, I had to say Brightcove, right? But honestly for me it’s more about content. I’ve been watching a lot of old Nova shows on Google Video lately. One cool thing you might not be aware of in Brightcove is the video search engine, which will return results from every major video service.