Probably there is more feminist fiction within the Science Fiction genre than in the mainstream. I have always been quite a fan of feminist fiction and have quite a collection of feminist science fiction novels.
Foremost of these is Suzy McKee Charnas' Holdfast Chronicles. I have the first three novels and have yet to acquire the last in the series "The Conqueror's Child".
They are a terrific read, set in a future where women are enslaved, and how one woman, escaping into the the wilderness plots, and eventually carries out her revenge.
Joanna Russ' best known book is The Female Man which I just realised must have been the inspiration for Sheri S Tepper's latest novel "The Margarets". I can't remember anything much about The Female Man, but having just read the wikipedia entry on the book, it suddenly struck me.
The Motherland Chronicles by Canadian writer Elizabeth Vonarburg are another feminist dystopian trilogy which began with The Silent City and also make for a good read.
Yet another trilogy... more lesbian fantasy than feminist science fiction, but quite enjoyable novels all the same.
Elizabeth A Lynn's Chronicles of Tornor
And to finish off this entry - the strange, yet compelling Mutagenisis by Helen Collins