I've been reading a book called Snoop by Sam Gosling. It's been interesting to read (I have one chapter left to go).
The idea of snooping is that you can find traces of the personality of a person based on the things they leave behind. He's studied bedrooms, offices, and websites (plus read research of people studying other things, like personal interviews or social behavior).
Interestingly, the best place to learn about people is their website. You can find out how open to new ideas they are, how organized they are, to some degree how much of an extrovert they are, and how uptight or nervous they are (I am way watering down what the book has to say, I'd suggest just picking it up and reading it). Websites, however, will not tell you how nice to be around someone is.
Let's see if you can tell me anything about my personality (based on what you've read from my writing). Anyone who's right will get a virtual hug. Anyone who's wrong will also get a virtual hug. And if Dr. Gosling happens to stumble across this, I'd love to know what I'm telling the world with my blog (not that the world is generally reading it), so please let me know.