Here's some exciting news from HearJapan, a Japanese music importer: they've worked out a deal with Vocaloid2 and the KarenT music label to release the music of Miku Hatsune, Rin and Len Kagamine, Megurine Luka, and Gackpoid. (I couldn't find an album with a specific reference to Rankapoid, aka Megumi Nakajima's Megupoid, but some albums claim to have “all” of the main characters featured, so she might be on one. Some of them even feature the original Vocaloid engine's Meiko and Kaito characters.
The tracks were created by various mix masters in Japan. Full albums generally contain 10+ tracks and cost about $9.54-- although the system actually uses yen. (¥900 per album, single songs are about ¥150). You add money via Paypal or WorldPay, so the American equivalent will actually be calculated on a day by day basis and, as such, will vary over time. (Currently ¥900 is actually about $9.59.)
Right, anyway! You also get album art with each album purchase, and there are samples of each song, so you don't have to buy blind. I picked up an album myself pretty smoothly, and you can actually download each item up to three times, and there's no DRM either. Good stuff!
For the record, the Tennessee Tunes single is pretty cheap and the first song, which I'm listening to right now, is fairly catchy. If you want a place to start! Another place to start: the full listing of Vocaloid albums.