I`m not in design or graphics, but represent plenty of clients in those industries. They range from solo start-ups like yourself to fairly big companies. I`ve worked with all of them since they were in your position, trying to figure out where to land those first clients. My best advice is to embrace some good old-fashioned networking - get out there and meet people. Attend small business forums, workshops, etc. Your target audience - especially on the design side - will be small business owners looking for someone to design their first website. Take on a couple of projects for little to no money - use them to build your portfolio and word of mouth. I see from your profile that you are in Chicago - there are probably tons of networking outlets and events for you to attend. As for finding business on the software side, you`ll want to network in a way that is more specifically geared towards the technology industry. The same principles apply, however - meet people, get business cards, follow up.
I agree with both of the reply posts given here - network - network - network. However, if you feel like this isnt working for you then pay a company to do this for you. This can be an effective way of targetting certain areas and channels and they can sell up your services. However they all cost money depending on how much you want them to do.
I`ve used a public relations firm since I started my practice four years ago. I found a guy who had recently left a big pr group and was starting up on his own, as well. His fees weren`t too bad, and he understood what I needed, which was exposure to the local market. I found that press releases were the best way to get noticed in that regard. We would send out releases whenever we did anything of substance. I honestly can`t tell you how many times someone approached me in those early days and mentioned that they had seen our releases in the local paper or a local trade publication like the Business Journal. There are online services that I have run across as well which can handle press releases on a flat-fee basis. And, to be honest, you can do them yourself.