I’ve got an Anker A7908 speaker (edit – also known as the classic, I think, that johnners mentions above) and it’s very good for the money. I think it was £30 when I was bought it as a present, but it’s currently on sale at Amazon for £22.
20hr battery life, which seems genuine – I hardly ever have to charge it.
Sound quality is decent & perfectly capable of enough volume for listening to around the house, out in the garden, in a holiday apartment etc…
The only thing that annoys me about it is the beep it makes when you turn it on is quite loud & you can’t stop it from doing it. But, a minor issue in the scheme of things.
Here’s a link:
http://www.amazon.co.uk/Anker-Portable-Wireless-Bluetooth-Microphone-Black/dp/B00GZC35YK