www.moneysavingexpert.com does this, for instance. As well as the '*' by links, they also have a better description at the bottom of the page explaining the aff

www.moneysavingexpert.com does this, for instance. As well as the '*' by links, they also have a better description at the bottom of the page explaining the affiliate links, together with direct links for people who don't want to use the affiliated ones. e.g. http://www.moneysavingexpert.com/insurance/cheap-travel-insurance http://www.moneysavingexpert.com/insurance/cheap-travel-insu... (a big page, but look at sections 14 and 16 for link examples)