What I am about to say is my own personal opinion and should not be considered affiliated with anybody but me.
My personal opinion is this: Once you take the step to start selling your books, establish an online presence. Preferably a website, a blog, or even Facebook, just somewhere you can list your books. Because if I don't know what books you have written, how do I know what to look for? And if you're a published author, that list should be current.
Authors with no websites or inaccurate bibliographies has long been a peeve of mine. During my Borders days, sometimes I wanted to double-check something about an ARC I read and I couldn't because the author's website didn't have any information about the upcoming title yet. Sometimes I loved an ARC and wanted to see what else the author had out, but couldn't because there was no website, it wasn't current, or didn't feature a bibliography. You're an author. I shouldn't have to go through a scavenger hunt just to find out what you wrote.
Now that I'm internly, this makes me more aggravated. You're trying to break into a very crowded, in flux, market. You want an agent to represent you through these rocky shores. Who you are is almost as important as what you write. If you have a lot of twitter or blog followers, this is a point in your favor. It means you already have a potential market. If you have free fiction up, this gives us a taste of what you can do besides what you sent in. If you've been signed by an agent, put their information up on your contact page. This tells me you've already been signed by someone else and if any editors happen to like your stuff, they can send your agent a feeler about what you might be shopping around.
Don't get me wrong, I'm not saying you have to code every line of HTML yourself. I can think of five authors off the top of my head who use a PR firm to do giveaways and contests or have a webmaster to run their site. You can be the Great and Powerful Wizard of Oz while someone else is the man behind the curtain, but you still have to build the Emerald City so Dorothy won't be left stranded on the yellow brick road.
Take pity on Dorothy. Have an online presence.