I learned about a Firefox plug-in HTTPS Everywhere yesterday and immediately fell in love with it. To help you be more secure online it rewrites selected URLs (e.g. Dropbox, GMX, Google search, Paypal) from http:// to https://. The selection can be configured and extended by custom rules. I wonder how I managed to not hear about this thing earlier. Interestingly it comes with built-in support for Gentoo. If you haven't tried it, please do.