AFAIK, there are 3 products currently available here for WB calibration on our DSLRs - the expodisc (both the netural and warm versions), one from PPCP and the other marketed by perly inc.
i know abt the expodisc - currently the priciest WB tool on the mkt. i would like to ask if there are folks who are using the other 2 alternatives, and find out how the products are? i used to have this piece of fresnel plastic marketed by another CSer during a MO. sadly, the product is not effective for me. ended up giving it away.
i also have a WhiBal card... but it's a bit of a hassle to bring it out cos i've to keep it in my pockets. sometimes, my bermudas dun have pockets deep enuf for it.