My most used bike ride swag has been a little microfiber pouch for keeping my glasses in and a bottle cage carrier that I put my tools/tubes in (like a cage rocket, but a little less high tech). Other little nifty items have been custom lip balm and a little zipper pull thermometer (both from the Chilly Hilly -there's a theme ).
Water bottles are usually the wrong size for my bike and tee shirts I have a plenty, but socks do sound like a fun idea.