Recommendations for external SSD boot drive please.

I'm a fan of the Samsung SSD's and would recommend the 840 EVO.

I just bought a crucial mx100 512 gb ssd for the purpose of boot. I want osx and windows bootcamp on the ssd. Can anyone provide a tutorial?

If you want to boot from Windows via an external drive, I believe your only possible choice is thunderbolt, because to my knowledge you can boot Windows via USB.

However,
IF you can forego booting Windows externally,
and
IF your iMac has USB3,
then
... a USB3 external enclosure or USB3/SATA dock would be a cheaper way to put together an "external booter".

There is a nice external 2.5" enclosure by a company called InaTeck (Germany?) that's cheap and runs well (has UASP support, which you ABSOLUTELY want in a USB3 external boot enclosure).

There are several USB3/SATA docking stations that also have UASP support.

But again, if you have-to-have Windows booting as well, your choice must be thunderbolt, and those choices seem to be relatively limited...

I'm doing a thunderbolt connection. Yeah I want both windows and osx on the external ssd. I've read about using winclone for moving the bootcamp partition from the internal drive to the external ssd. But I also want osx on the ssd as well.

I bought a Lacie external SSD with Thunderbolt and USB works well as a boot drive for me. My only complaint is the small drive size.