I bought this cute case for the Raspberry Pi.
It's made by Italian company Italtronic, in the UK avalable from CPC.
They have cases for different Pis. Mine is for the B+.
It's easy. There's no Ikea-style manual though, so you may get it wrong the first time.
The only tool required is a screwdriver. The Pi is locked in place with 2 screws (included).
Some attention is needed:
It's beautiful. And of good quality.
What I'd like to have seen is:
Overall, a nice and not-expensive option if you want to rail mount a Pi.