Two major releases recently.
Linux Mint has released version 11 - if you want a "windows-like" alternative experience then this may be the one for you.
Looking at it, it seems very slick and dare I say it, more Windows than Windows!
Then again there's been a new release of Ubuntu - 11.04.
This has replaced the standard Gnome desktop with something called Unity - a desktop manager that isn't to everyone's liking but is certainly different, and I think, innovative.
Both can be booted from a Live CD, and both can be installed (and booted from) an external disk or flash drive - take your favourite version of Linux with you!