Update: Since this post was written, Hotmail has added proper POP3 support – see this entry for details. The instructions below are therefore unnecessary.
I’m now using Thunderbird’s Webmail extension to check my Hotmail account, which is usually full of gunk but occasionally has something important in it.
The extension is very slick – it’s a case of downloading the core package plus the package for the particular service you’re using – Hotmail, Yahoo or Lycos – installing them, restarting Thunderbird and then setting up the account. It even integrates neatly with the Account Settings wizard so it’s no more difficult than setting up any other email account, and doesn’t require you to run any external programs. And unlike other tools like Hotmail Popper it’ll still work with free Hotmail accounts.