There are only few things you can do to make it harder for the people to find your internet trail.
You have an email? Change your info to some random info, save and then cancel it. Same goes for similar accounts.
You have an e-banking account? Demand your bank to disable this specific service for you.
MSN? Cancel it.
Facebook? Erase any trail left (for example pictures, notes, friends) and then cancel. DO NOT DE-ACTIVATE, CANCEL THRU HELP ME.
Skype? Cannot be canceled but you can alternate your real profile to a fake one.
Have a personal website? Cancel it via the hosting company.
Remember everything can be cached to search engines or web-servers or can be saved to local hard drives. Example, I posted my pic on facebook, some friend of mine saved it on his computer, nothing can be done about it.
That’s all you can do to protect yourself. And of course IP logs are out of the table.