This isn't meant to be an all inclusive list ... just a few ideas to get your juices flowing ... and your hind quarters up and moving.
Social networking is a no brainer. I won't spend time on that subject as you can find specific articles with plenty of detailed advice perusing the archives of Small Business Resources Cafe.
That said .... lets look at your other options.
If it is a local brick and mortar business, the newspaper is actually a great place to start. It is an old school tactic, but it works.
On that note, news in general is a great way to get visibility. So, Press Releases are really effective. You can submit a press release to many PR sites that talk about the launch of your business, or a new solution your business is providing. It just has to sound like news. You can find several press release templates through a Google search.
I also found an article on this subject. A number of places to submit your website for free exposure. Here's the link ....
Top 7 Websites to Submit Your Startup Company to for Free Publicity
Events are also a great way to increase visibility, but that will be limited by the budget you are working with.
Don't forget branding. Location based service giant Foursquare offers you the opportunity to utilize their services as a Brand. This is a fun and cutting edge way to get your name out there.
There you go .... not too complicated. Just some simple actions anybody can do .... you just have to "do it".