I made several of these (Gina K Designs). Quick and Easy, and fun to see the gift card pop straight up when you open the wallet. Here's the tut:
Gift Card Holder - Part 1 - stampTV
Gift Card Holder - Part 2 - stampTV
These fit in my smaller envelopes, which I embellish to match the gift card holder.
And I made a dozen of the ones like Diane's (used Cherry Cobbler for the cup, to resemble the Starbucks winter design). These fit nicely in a regular A2 envie.
I also modified my usual A2 size...since I use a large sheet of card stock for my bases (11 x 17), I just added one inch to the length, so I could score that inch, fold it up, using Sookwang tape to adhere it. This makes a perfect pocket for a gift card or cash. So, I either cut my base at 4.25 x 12 (that extra inch is what makes the pocket) for tall cards, or 5.50 x 9.50 (again, that extra inch will fold up for the pocket. Here's an example from my gallery (it's my step-son's birthday card):
Card for James by kitkat55 - Cards and Paper Crafts at Splitcoaststampers
Hope this helps!