The simplest answer is the Internet. It has been an invaluable tool to me for my marketing. However, this may be a slightly too broad and generic answer to be of much use, so allow me to expand.
I started my own blog, and while I struggled with it at first, I have gotten things down now and am really enjoying managing it. I interview people, post my own thoughts share those of others, and while I have not sold many books directly as a result of clicks from my blog. Traffic is increasing every month and my network is increasing in size on a daily basis. The blog is not a sales generator, but a platform that I base my image on. It is an invaluable tool to any writer, but especially one who is self publsihed.
Facebook is another great tool for both networking and sales generation. I have a profile that I manage for my networking, and pages that I use for sales. When combined the two Facebook approaches make a powerful tool, which can easily be coupled with your blog.
It takes time, it is not an overnight endeavor. I always remember the quote, "Overnight success takes 10 years." and this is true. It is a long read and takes hard work and dedication. Without the willingness to sacrifice and give 110% the rest ultimately becomes meaningless.