My favorite find so far is "Advances in Crypto" conference proceedings going back to the early eighties:
- http://link.springer.com/search?query=%22advances+in+cryptol...
- http://link.springer.com/search?query=%22advances+in+cryptol...
- The Design of Rijndael http://link.springer.com/book/10.1007/978-3-662-04722-4