My answer follows:

• ~/Applications/ : for apps that I like/use etc beyond the standard Apple preinstalled set
• ~/bin/ : for command line tools (usually ones I wrote myself)
• ~/Documents/ : for personal info
• ~/Development/ : for work projects, Open Source tools, etc
• ~/Temp/ : for temporary items that I don't feel bad if I lose or don't back up. Downloads go here too.

Feel free to answer the QTOD in your own blog, in the comments here, or over at Mike's site