The marketing scheme aims to draw more visitors to tourist attractions across Oxfordshire, Berkshire and Buckinghamshire.
It is built around a website which lists the addresses, opening times and admission fees of all the venues.
Each member has been given a TV screen worth £130 which will show a video promoting other destinations in the area.
They will be encouraged to use the Thames Valley Museums logo on their advertising and promote themselves on Twitter and Facebook.
The River and Rowing Museum came up with the idea last year and secured a £50,000 Arts Council grant.
It teamed up with Tourism South East, which provided a project co-ordinator, and approached other venues.
Among those taking part are Stonor Park, the ancestral home of Lord and Lady Camoys, the University of Oxford?s Ashmolean Museum, Wallingford Museum, Didcot Railway Centre and Cliveden house and gardens, near Maidenhead.
The River and Rowing Museum will remain in charge of the project and will offer marketing advice to the smaller venues.
Paul Mainds, chief executive of the River and Rowing Musuem and chairman of Thames Valley Museums? chairman, ?We reckon we have over five million visitors a year to our museums already.
?You can all do the sums - a one per cent increase will do. Two percent would be 100,000 and why shouldn?t we do more??
Mr Vaizey said: ?It?s wonderful to be in this museum, which I?m ashamed to say I haven?t visited before. Not only does it have an amazing collection but it is a wonderful building.
?As minister for architecture, it?s great to see David Chipperfield?s first museum in Britain here in wonderful Henley.
?This project is long overdue and it is pioneering, so a big thank you is due to everyone who has made it happen.?
The minister told the Henley Standard: ?I am passionate about different organisations that do the same thing collaborating. By coming together they can reach much bigger audiences and they can learn from each other.?
Project co-ordinator Jeanette Howse said: ?A lot of these museums are quite small so they don?t always have the resources to promote themselves. Some are so small they don?t even have a website.
?This gives them an opportunity to increase their footfall through a funded project.
?The River and Rowing Museum team have done an amazing job when you consider that they?re also running a highly successful museum every day.?
For more information, visit www.thamesvalleymuseums.org