We updated the faq for this recently, based on:
Limits for self-promotion in answers
May I promote products I am affiliated with here?
Be careful, because the community frowns on overt self-promotion and tends to vote it down and flag it as spam. Post good, relevant answers, and if they happen to be about your product, so be it. However, you must disclose your affiliation with the product in your answers. Also, if a huge percentage of your posts include a mention of your product, you're clearly here for the wrong reasons. Our advertising rates are quite reasonable; contact our ad sales team for details. We also offer free vote-based advertising for open source projects.