I'm currently designing a wildlife pond and I want to ensure I have something for everything. Not too mention i just love watching the bees bopping around while i'm working in the garden.
I have Calth (marsh marigold) which is a very popular bog plant and loved by insects of all kinds. Easy to get hold of and easy to keep. The Loosestrifes are also good - there are yellows and purples. Ligularia is good for a damp spot but likes a bit of sun - they have orange/yellow daisy flowers which bees and hoverflies love. Some have spikes of flowers similar to an Eremurus. Most GCs will stock one or two types.
There are loads but hope that gives you a couple of ideas to go on with.
Puddleplants are a good resource. Not cheap but good quality and their website gives lots of information.