Seniors, I have other sites that are loaded with singles from ages 40-75 looking for that special someone. I have one devoted to seniors site listed. The others are full of single seniors, just do a search based with the age range your looking for, and you'll find plenty.
Senior FriendFinder -Is the most popular place for people over 40 looking to meet others for romance, dating, and more! Signing up is free, and certainly worth checking out.
Big Church - a faith based dating service, growing...and quickly. Many great people to browse, and pen pal, or have bible study with. Respectable and mature.