Just to be even more of an enabler...
Here are a few cards from the gallery here on SCS that I think use washi tape really well.
Forever and Always by ~Fee~ - Cards and Paper Crafts at Splitcoaststampers
Milestone Markers by tayloredexpressions - Cards and Paper Crafts at Splitcoaststampers
Home Sweet Home by mom2n2 - Cards and Paper Crafts at Splitcoaststampers
Hugs, Hugs, Hugs by khowardga - Cards and Paper Crafts at Splitcoaststampers
And here is an Etsy shop that sells it in various quantities: Colorful Washi Tape Masking Tape and lots of sticky by StickerStop
I have no affiliation with this shop whatsoever...I think I picked up the link from the fabulous and talented Julie Ebersole's blog: Paper Trufflez
I think Julie's blog is where I got my first glimpse of it in action. I've bought a few rolls so far at Michael's with coupons. But I still have some Christmas money left and might be placing an order at the Etsy shop I mentioned soon!!