If you want to stick strictly to the Internet take a look at ezine classified advertising. Here you will find an audience that has asked to receive the ezine. They actually read it and are more responsive than people just surfing the net. There are many ezines, which do accept free classified ads, and many, many more which charge a very nominal fee.
Every one of these outlets will charge by the number of words or characters, so keep it short. Use your URL for contact. It is not advisable to use phone numbers or e-mail addresses, unless you are prepared for possible telemarketers and/or spammers.
Keyword Elite: Generate 1000s Of Keywords In Seconds!