Just thought I'd share this...
A popular argument against evolution is that it has never been observed... Well, I recently came upon an article on the Discovery News website that shows evolution in progress. Threespined sickleback fish that live in a Washington lake lost their bony armor when they migrated to fresh water. In the 1950's and 60's, it was observed that the unarmored fish were almost a complete majority. When samples of the fish were collected recently, it has been observed that the freshwater version of the fish now has plates, with fewer than 16% of the fish possessing few to no armor plates. It is believed that the fish redeveloped the armor after the lake was cleaned, removing the murkiness from the water. This exposed them to predators.
LINK