The below is a number of toolbar buttons that will open various pages. If you would like to create your own you can use the Custom Link Button Maker. The links in all these extensions can be changed in their options window after beings installed.
Open eBay online shopping
Opens Twitter a Social networking and microblogging service.
Open Mozilla's Firefox themes website.
Open Reddit, a site of user-generated news links. Votes promote stories to the front page.
Open Hacker News, a social news website that caters to programmers and entrepreneurs, delivering content related to computer science and entrepreneurship.
Opens GitHub, the best place to share code with friends, co-workers, classmates, or even complete strangers.