In no particular order, and with no guarantee of usefulness or truthfulness, I have found the following websites useful and/or interesting:
United Kingdom Council for Psychotherapy
British Association for Counselling and Psychotherapy
Site for those suffering from anxiety
Mad Pride, campaigning for those with mental health issues
Dept of Health mental health pages
Moodgym – online resource to help cope with difficult feelings
Big White Wall – a place to share difficult feelings
Royal College of Psychiatrists mental health information
Black Dog Tribe – resource for those with mental health issues
Relate – relationship counselling
Rape Crisis – support for victims of rape and sexual abuse