Trapit - A Google, Newsletter and Wikipedia Mix
I came across Trapit yesterday, I don't remember how, but anyway, it's rather good. Still in beta, I should imagine it'll get very good, especially if you can use boolean terms to search with, but as it is now you just type in something you'd like to know more of, and off it goes to scour the web and bring back juicy information.
You can create multiple 'traps', which are the subjects you want to know more about, and can choose to have an update every day which is delivered to your inbox. A mix between Google, newsletter and Wikipedia.
Check it out, I think it's pretty useful.