On Captcha's, and Analytics.

Captcha's are a sort of reverse Turing test. Instead of humans trying to call out computers, computers are trying to call out computers. The idea's easy enough. To prevent the endless torrents of spam from form submissions, you could make a simple human test to make sure the submissions are from people rather than bots.

Here are some different implementations. I'll update this list if I find any other clever solutions.

• Official Captcha - CMU was first to write a paper about it. They also have this great project called reCaptcha that uses bad OCR images of books being digitized. This can help with efforts to digitize crumbling literature! On top of that, they provide an accessible captcha for the visually impaired by reading out the word.
• Logic Captcha - Instead of using an image, generate some trivial arithmetic problems, or simple trivia problems for the user to solve
• Honeypot Captcha - I'm a fan of this one too because of it's clever use of CSS. On top of being accessible, it's completely idiot proof because the user passes if he doesn't do anything! The way it works is to have an extra form input field that's hidden by CSS. A mere mortal would simply skip this field and leave it blank, but a malicious bot would fill it in anyways. Simply discard all POSTs where this field is filled.

Mint looks like a very promising, and very cheap solution to do site analytics. Google also provides a free analytics tool that pairs up well with their Adwords program.