This page lets you select an affymetrix chip and will return the closest phylogenetic relative for the species you specify. (i.e. select the ATH1-121501 Arabidopsis chip and specify "Arabidopsis ATH1-121501" in the upper text box and "Solanum tuberosum ; Lycopersicon esculentum" in the lower and the output will contain a list of all consensus sequences on the ATH1-121502 chip with their putative orthologs for Solanum and/or Lycopersicon.)
For more information go HERE
NOTE:If you are using internet explorer you may have difficulties viewing the results. This page has been tested and works with any of the more standards-compliant browsers (such as firefox, opera or safari).