I've just discovered Evernote and I think I'll be using this service a lot. It combines online notes, bookmarking, character recognition and a filling system to create a very efficient way to capture and organize your thoughts, observations and all those things you need to remember. There are a couple of versions of Evernote, I'm using the 3.0 beta which is Web (and mobile web) based, although it also has a optional desktop component. I haven't tried the older desktop-only 2.2 version. The 3.0 beta is currently "closed" but that just means who have to request a invitation which can take a few days. The invites seem to be all over the web lately, in fact I have 20 to give out. Leave a comment if you want one.
The way Evernote works is that you send "notes" to Evernote. The notes can be Web pages; snippets of text from a page, email or document; images (especially those containing text) or PDF's. To send notes to Evernote you can use a bookmarklet, email, MMS or Evernote's Mac OS, Windows Mobile, XP or Vista clients. Java ME and iPhone clients are under development. The Windows and Mac desktop applications are complete standalone note management systems that can obtionally synchronize with Evernote on the Web.