Mixture, produced by Kaori Minakami (水上カオリ) is a gorgeous collection of Vocaloid illustrations inspired by the Vocaloid original songs themselves. This doujinshi was released during Comiket 76, is 24 pages long and entirely in color.
Momose Hisashi's Rio Miku is a collection of illustrations of (you guessed it) Hatsune Miku and Rio de Channel that span a few years for this artist. Though more familiarly known as Momo, I kept the artist's actual name for the category because it's a lot easier to search for than just "Momo."
During Comiket 76, Itoh Ben (伊藤ベン) released his completed Typemoon Laboratory [ -Ver. Fate- ] doujinshi. I say completed, because for Comiket 75, he released the Typemoon Laboratory [-Preview-] which is nearly entirely included in the finished one. So if you were picking between the two, definitely get [-Ver. Fate-].
Ever wanted one of those huge anime girl pillow covers, but didn't want to pay that much for it? Or better yet, ever wanted a dakimakura, but didn't want to admit to wanting it and so hope to someday unintentionally acquire one? Well, make sure you buy this month's Dengeki G's Festival Anime magazine.
Pandora Hearts ~odds and ends~ by Jun Mochizuki just came out at the end of last month and is a huge, 168 page collection of Pandora Hearts art work, with a little extra. The book itself is really thought out with design pages, cut outs and colors to best present each illustration.
Nagi Ryou (凪良) is probably best know for the game designs of Ar Tonelico. And if you haven't seen those, then he's probably pretty new to you. Nagi Ryou also has a circle called S.E.C., though as far as I know he's the only one in it.
Influence was a Comiket 76 release, featuring Nagi Ryou's take on anime and art work that influences him. I would guess Neon Genesis Evangelion was the greatest influence as it gets the most pages, but of course that might also be coincidence.
Buying doujinshi can be quite expensive when you bid on already inflated auctions, where you'll still have to pay for shipping, service fees, and wire transfer fees through a deputy service.
While auctions are great for buying truly rare items, you should always check Japanese online stores like Messe-Sanoh, Toranoana, Melonbooks, and Mandarake before placing a bid. Not only can you get an idea of the "retail" value of a doujinshi, you can also see if they happen to have it in stock. All of the shops mentioned except for Mandarake, only ship internally (to Japan addresses). To work around this, deputy services--companies that buy these items on your behalf for a service charge--are plentiful.
nattoli.net is a blog of anime art book, magazine, and doujinshi reviews. In the mix you'll also find wallpapers, opinions, buying tips and my thoughts on collecting art books.