IMA - the Investment Management Association. Most of the really useful information on taxation etc. is on the member's only pages. Publicly available information includes regularly updated figures for funds under management of member companies and the EMX site with regular monthly progress reports.
Compliance Exchange - a most useful site for compliance and administration professionals giving the latest updates and an excellent source of information for all things compliance
Compliance Online - another very useful general compliance site with news updated daily and various information sheets
CrestCo - market practice for Unit Trust and OEIC settlement
Data Protection Registrar - all unit trust managers have to be registered, you can check your registration at this site
Financial Times - the archive is really useful for searching on financial topics with over 5 million articles available from 3,000 organisations all round the world
Inland Revenue ISA site - for the handbook and latest bulletins on ISAs
Mondaq Business Briefing - provides business briefings on legislation and regulations
PIMA - PEP and ISA Managers Association
Securities Institute - the main professional organisation representing the securities industry. It provides FSA recognised exams and training courses for unit trust and OEIC administration
Stamp Office - provides guidance on the application of the new SDRT regime to OEICs and unit trusts
Winchester White - the highly regarded insurance and investment consultancy recognised for using very experienced market practitioners
Software companies:
Bank of New York - produces RUFUS
COR Systems - produces CO-STARS
WMS - produces LISA
MFTL - produces GFAS
Linedata - produces Fortis
FundSoft - produces Cobas
Tacit - produces Talisman
Third Party Admin companies:
International Financial Data Systems