Two dating websites that allow women to seek out women are OKCupid and Plenty of Fish. These sites are completely free and allow users to seek out same-sex potential partners.
OKCupid allows users to specify their exact gender and sexual preference and exclude those who do not match from the search results. Users can answer questions and note how important the question is to further narrow down their matches to the most compatible profiles.
Plenty of Fish has a simple registration and a single chemistry test that helps match users up. Users can also search results for specific interests to find those with similar hobbies.