I recently just realized that my gmail account provides what they call "last account activity". It lets you know the ip address that last accessed your account. It is located all the way at the bottom of the screen. If you click on the link, it will give you information on the ip address and how it was accessed (via POP3, browser, mobile, etc...) It also gives you the option to sign out all other sessions. For example if you were at work checking your email, then you get home and realize that you never signed out at work. This feature is sooooo important for me since I recently found out someone had installed a keylogger in my computer and was accessing my e-mail and myspace accounts.
I was wondering if anyone knew if yahoo offers the same service/feature. I tried looking but did not find anything.