In recent years, a handful of developers have attempted to add note-taking capabilities to Gmail, the idea being to let you attach custom, personalized information to any given message.
For example, suppose you get a sales inquiry from a potential customer. You could attach a note with details on when you replied, what you said, how you plan to follow up, and so on.
Likewise, if the boss emails you about an important project, you could embed related information inside that email rather than keeping it someplace separate. Heck, maybe you just need to remind yourself who the sender is, like if it's someone you met at a conference. The possibilities are fairly endless.
Notes for Gmail is a new browser plug-in that, in case the name didn't give it away, lets you add notes to Gmail. It's a simple but incredibly useful tool, and for the moment it's free.
It's also in private beta, though I was approved immediately after clicking Request an Invitation. Your mileage may vary.
For the moment, Notes for Gmail works only in Google Chrome, though a Firefox version is coming soon. Because it's not yet live in the Chrome Store, you'll have to install it manually -- which isn't complicated, but you'll definitely want to follow the instructions if you're not familiar with the process. (In a nutshell: Download the add-on, open Chrome's extension manager, then drag the add-on to it.)
Once it's installed, it couldn't be easier to use: Just open any email message and then click Add Note. You'll get a blank field into which you can type or paste your info. When you're done, you'll see the equivalent of a yellow sticky appended to the top of that email.
Mouse over the note and you'll see four options: Facebook, Twitter, Delete, and Edit.
The developers promise to add more features in the future (I'd like to see a date/time stamp), and probably a price tag as well: The product page notes that the service is "currently free," meaning it probably won't be once it leaves beta.
Which begs the question: How much would you pay for Notes for Gmail? I definitely think it's worth something, though I'm not sure I could see myself paying more than, say, $20 annually. Your thoughts?
While we're on the subject, check out Three Ways to Make Gmail Easier to Live With.