I get the majority of my stuff from Pixiv.
You need an account there, and also a decent understanding of Japanese (Or just a good translator - Google Translate does the trick when using Chrome). I recommend that you use the tags listed with works instead of typing them in yourself as they tend to not work how you might imagine them to (Most of the tags are in Japanese, you see).
Once you have that, it's an excellent resource. Danbooru and Gelbooru often don't note some of the more obscure works on Pixiv, although they've been better about it lately.
http://www.pixiv.com - Beta version, has some English support
http://www.pixiv.net - Original version, pretty much entirely in Japanese but is a lot more standardized.
