Google search your name. This will not show your best face, but should give potential clients a good picture of who you are. You want to be active in the community, posting on forums, and you should have a blog.
Aside from starting your own Rails business, there are good reasons to start blogging. There are companies (e.g. Industrial Logic) that will not even consider a developer for employment if they do not own a blog. The other side of this coin is that you can weed out potential employers that don't read your blog.
Also, aside from considerations of self-promotion, there is an even more important reason you might want to blog. ThoughtWorks illustrates the impact of developers having a strong written culture.
Traditionally, companies will reward their Sales employees handsomely. (There are many reasons for this, but one interesting one is that it's really easy to measure the contribution of a salesperson; less so, for a developer.) Because of how they are compensated, sales staff are motivated to seek out the largest companies with the biggest contracts. This is really good for sales staff, but can produce really bad customer relationships for developers.
ThoughtWorks is a good example of how a strong developer voice has compensated for the strong forces that produce Sales-driven organizations. They have fostered a culture of writing among their developers. The company's blog is just an aggregation of all of their developers' personal blogs. Martin Fowler isn't even billable; he just writes books. People know of ThoughtWorks because of their developers (e.g. Martin Fowler, Chris Stevenson, and Obie Fernandez...although Fernandez is no longer there). ThoughtWorks has shifted the sales role to their developers.
So, blogging is self-promotion, but it's also a subtle mechanism for selecting the quality of your relationship with your customer...start blogging.