Here are some sites you may find helpful for your own research. I’ve split them into different areas. If you have any suggestions to add please let me know.
The Family History Federation has a searchable list on its website here. This can also be viewed as a map.
Forebears is a directory with listings which take you to other places. It can be filtered by county and will tell you where the relevant records are held.
GENUKI also has a directory of lots of different societies here. This includes Jewish records, Romany records, the Quakers and some societies in other countries.
The Scottish Genealogy Society have lots of records including the original microfilms for every parish in Scotland. Plus a comprehensive library and a collection of donated family histories, pedigrees and research notes and lots more. You can also visit the society at the Library & Family History Centre in Edinburgh. They also host talks and run courses.
For anyone with Huguenot ancestors the Huguenot Society is a good starting place. There is an online library (hosted by UCL) and you can visit the Society in its London headquarters.
There are a couple of good starting points for tracing Irish ancestry:
Irish Genealogy host church and civil records (I found some of my missing ancestors on here). There are Births, Marriages and Deaths from the General Register Office and the Indexes to the historic records of Births, Marriages and Deaths in Ireland. The records are free to view online.
Roots Ireland is a subscription service containing Catholic records. A subscription can be as little as one day.