X-link to the Comics thread for some sfnal bundles:
Humble Book Bundle Science Fiction Manga by Nihei contains titles by popular manga creator Tsutomu Nihei, published by Kodansha. There's an entire set of his
Knights of Sidonia series (also adapted into an anime) at the top tier, and you can get a freebie by signing up for the newsletter.
Also, there are some sfnal series in Groupees'
Top Cow Bundle, which at the $15 top tier will give you at least 2 volumes of most titles.