Put your references in a common place. Then set the property CopyToOutput to 'never' (or 'if newer'). But you'll need to be sure the path where you put them is in PATH or something, otherwise they will not be found.
You can embed your dependencies in the exe. There are ways, like treating them as resources and unpack at runtime.
Or you can use this tool:
CryptoObfuscator
About post-build steps:
http://geekswithblogs.net/dchestnutt/archive/2006/05/30/80113.aspx[
^]