Interesting Firefox extensions

In the absence of anything more interesting to write about, here are some Firefox extensions that I've recently installed and found useful or interesting:

1. Effortless Good - automatically adds an affiliate tag for products bought at Amazon, with the income donated to 4 charities. Doesn't overwrite normal affiliate links. Means you can do good with minimal effort.
2. FireGPG - integrates GnuPG with Firefox, and in particular Gmail. You can encrypt, decrypt and sign the contents of a text box or emails. Requires GnuPG.
3. ForceHTTPS - ensures that you're using the encrypted (HTTPS) version of popular web sites like Gmail and PayPal where you share personal information.
4. firefox-mac-pdf - allows PDF files to be viewed from within Firefox on a Mac, rather than in Preview. Mac-only.
5. YouTube Comment Snob - hides idiotic comments on YouTube videos.