http://whofundsyou.org/
They rate British think tanks and policy research organisations according to how transparent they are with respect to funding.
Their results are (with A being the most transparent and E the least):
This shows an extremely strong correlation between left and right, perhaps unsurprisingly! It'll be interesting to see how those rated badly react to their position (if they don't just ignore it).A – Compass, IPPR, NEF, Progress, Resolution Foundation, Social Market FoundationB – Demos, Fabian Society, Policy Network, ReformC – Centre Forum, Civitas, Smith InstituteD – Centre for Policy Studies, Centre for Social Justice, Institute of Economic Affairs, Policy ExchangeE – Adam Smith Institute, ResPublica, TaxPayers’ Alliance