la guida ad ajax si trova qui

http://javascript.html.it/guide/leggi/95/guida-ajax/


per quanto riguarda il tuo problema puoi trovare soluzioni analoghe qui

http://stackoverflow.com/questions/9...uery-ajax-post
http://codingforums.com/showthread.php?t=199428
http://old.nabble.com/sending-an-arr...150s27240.html
http://stackoverflow.com/questions/1...mysql-checkbox