Give away free educational/teaching/useful content that targets your customer - e.g. for our time tracking software, we have a fun paper printable time tracker for the "hipster PDA" and have several articles planned on freelance foibles / common time mistakes.

I'm pseudo-famous on the back of my Rails tutorials and cheat sheets.

This is way better than any kind of advertising you can simply plunk down money and buy, for obvious reasons -- it gets people to really like you, to spend the most time looking at what you make, etc.