How many versions/series of Milk-chan are there?
Two. The first is Super Milk-Chan, a series of 14 8-minute animations. This is also known as "Vintage Milk." The full-length spinoff that resulted is Oh! Super Milk-Chan, which is made up of 25-minute episodes. ADV has released both series on DVDs, along with an Americanized dub of Oh! Super Milk Chan (meaning the jokes are Americanized) which is titled The Super Milk-Chan Show.
Where can I buy Milk-Chan on DVD?
You can buy the DVDs from Amazon.com, among many other online DVD stores.
Where can I find mp3s of the Milk-Chan themes?
Right here in the media section of this site. :).