I find the newest Kindle (Kindle 3, as they refuse to call it) has a fine browser. You wouldn't reach for it if there were a laptop about (it's monochrome, smaller, it doesn't have a mouse, just directional buttons, and it can't open any link that want to open a new window) but it's about as functional as a modern mobile phone browser - actually it uses the same "Webkit" engine as all the latest Apple, Android, Nokia browsers. It's fine with dropdown menus (an old weakness, I think).
I can quite easily do my usual tasks on it - a look at Yahoo email (it writes them fine too), Facebook, a couple of news sites (Guardian, NYT, BBC), some google searching.