You need to know which. You won't help yourself at all, if your announcements are viewed as spam. You can sometimes get around this when you see someone ask a question that your page answers. Then volunteering the information is appropriate. Those techniques are usually seen through.
Web rings are another place to consider.
Web rings are a set of sites related by a common subject that link to each other and permit travelling around the ring in a circular pattern from site to site. You can search for existing web rings by topic at the main WebRing site . Review the sites in related rings and decide if you would like to be part of the ring. You have to apply, but if you have a good quality site, you will probably be accepted. The advantage of web rings is that it will bring new visitors to your site.