I can totally understand tight budgets, but one of the first steps to success in business is to start thinking of advertising as an investment.
Inexpensive ways to advertise are often in the realm of public relations - things like article marketing or sending out press releases. These provide a good return on investment. You'll want to make sure that you have a method of keeping in touch with former visitors and customers (an email newsletter does nicely) it's easier and less expensive to sell to someone who is already familiar with you and your services than it is to attract new customers so always keep your current customers in the loop and treat them to specials and start up a referral program so they're encouraged and rewarded for spreading the word about you. Word of mouth is the most powerful form of marketing...it's vital to harness that when budgets are low.
Eventually you will want to graduate to paid options in order to grow our business.
Most free advertising offers that offer tons of traffic for nothing, well the old saying of "if it sounds to good to be true, it probably is" applies. Steer clear of free options unless you've been able to check it out fully and have had a chance to check references and get feedback from those who have used the service.