ScratchBack is an online “tipping” system that allows you to collect tips and in return give the donor a link to their site, or a site of their choice. Go ahead and try it. Buying a link is about the same price as a cup of coffee.
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There’s a similar widget available from http://www.BringaBuddy.net which has a width of 160px and fits in most sidebars.
Check it out…