Firefox: If you've ever started up Firefox after a system crash and had it attempt to restore all the eleventy-billion tabs you had open, you know what a resource drain your tabs really are. BarTap helps alleviate the stress.
BarTap is a Firefox extension that keeps unfocused tabs from sponging up system resources. When BarTap is active you can specify that new tabs and restored tabs will not be loaded until they are actually clicked on, turning the tabs into placeholders for the pages you will be viewing and minimising the amount of system resources devoted to them. You can specify one action for restored tabs and one for freshly opened tabs if you prefer that newly opened tabs always load immediately.
Tabs that are on your "tap" are greyed out until you click on them. Clicking on them causes the content to load at the time you access them (as oppose to the time they were created). BarTap is a clever way to have a lot of tabs open without them bloating up your memory use. BarTap is free and works wherever Firefox does. Have a favourite extension for enhancing tabbed browsing? Let's hear about it in the comments.