Someone has posted a bookmarklet to email links with your default mail program, but for those who use Gmail as webmail, this will work.
Make a new bookmark and make the name Email with Gmail or whatever you want, and the URL
If you want a pop-up bookmarklet, use the following URL
That currently opens a new tab. I'm working on getting the pop-out effect that Gmail has.
Unfortunately, middle-clicking the first one does not work, because when it opens it in a new tab, it is reading the URL and title from that new tab instead of the original one you wanted to to link to. I may work on a solution to this in the future.
Oddly this makes the text box in Gmail not the width of the screen. I'm not sure why that is, but it works just fine- just looks a little funny. If anyone can offer any wisdom to this, I would appreciate it.