My email application of choice is gmail. My personal task management application of choice is Highrise from 37Signals.com. Our company also uses Basecamp for all our design and search marketing clients. One of the things I’d love to see is a way to add my gmail messages directly to Highrise or Basecamp. Basecamp already lets you email replies directly to the messages in projects and Highrise has a email dropbox so this can’t be an impossible task. I imagine that after clicking on the "Add to Highrise" or "Add to Basecamp" button a popup would appear with the email contents formated like a new message. The new popup would ask "Here is your new message/task, would you like to add it to Highrise/Basecamp now" or provide an edit function but showing all text as editble.
If you’re a developer with the skills to solve this problem let me know and we can figure this out together.