OMG! I found the best tutorial ever for Yoga/Pajama Pants on Craftster. I've made 2 so far from DH's old tshirts. I have a third cut out and waiting to be finished but I need to buy more shoelaces for drawstrings.
Super easy to make, and super comfy. I wear them all the time, and I don't for-see me buying pajama pants in the future.
I won't post the pics or the actual tutorial here, because I don't want anyone to get the impression that this is my original thought or project, but visit Tkrainy's thread on Craftster.org to see the tutorial.
I can't emphasize how quick and easy it was to make these pants. The lady who made this tutorial actually hand sewed her pants! The hardest part for me, was the waistband, and I chose to just add a drawstring then mess with pinning for an exact fit.