Communities - one of the biggest sources for 3D graphics. Free galleries, tutorials, diskussion groups with valuable tips and tricks from the community and also a big marketplace for hobby artists and professionals. A must for all who love 3D graphics.
Runtime DNA - A great resource and helpful community for all Poser related information. Some excellent tutorials and discussions about Poser 5 features (material room,...) and morphing. Also very nice items in their marketplace.
PoserPros - A wonderful community with excellent tutorials and almost perfectly moderated discussion groups. If you have a problem or question, just ask. You find also an excellent and professional marketplace for all kind of stuff. Have a look, you won't regret it. A subsidary to Daz 3D.
Daz 3D - Creators of the most popular characters for Poser, Victoria and Michael. Provide a lot of high quality figures and other content for Curious Labs Poser in their shop. They also host programs like Bryce 5.x and Daz Studio.
Content Paradise - From the people of E-Frontier. A community built around a big marketplace, which host famous Poser characters like Miki, Anton, Koji and Terai Yuki. They also host a forum.
Raunchy Minds - A page with art for adults, which you should only visit, when suitable and allowed for you. They provide a gallery, a forum and a nice adult/kinky community.
Renderotica - A vivid 3D graphics community addicted to adult erotic art. Restricted to adult visitors and with a wide variety of works from erotic art to bondage and fetish. The marketplace provides a lot of different items, but is spezialized on erotic and fetish items. If you are old enough and do not mind the dark side of passion, then give it a try.