I've used google alerts in the past, and thought it was pretty cool.
You can have google tell you whenever it find a phrase someplace new, like "trade show marketing" mentioned in a new blog post somewhere.
You can also have it tell you when it finds a new link to your website, or someone else's website.
But it seems like lately it's not sending out very many alerts, even though I know new alerts should be generated. It's almost like it's being throttled or broken. Does anyone else notice this, or are you guys even aware of google alerts?