I found a fun idea at Before and After Magazine with a new twist on making address labels that includes both the main address and the return address, as well. I just had to make one to try it out, so I thought I would share the fun with you.
The tutorial is a little "rough around the edges" if you know what I mean....but I think you'll get the idea ;)
Here's the label I designed [and no, that's not my real address].

Here it is applied to my envelope. [not the best pics...sorry...I really do need to make a lightbox, so I can give you better photos for my tutorials......someday :) Trust me, it's much cuter in real life.
Front

Back

You'll need Photoshop or Corel or some other graphic design program or you could do the whole thing free handed too!
- In Photoshop go to FILE>NEW
- When the Dialogue Box appears type in the dimensions you want your label to be. I used a 5x7 envelope, so I made my label 6.75" x 1.5". Check the size of your own envelope and adjust accordingly.
- Once you have your new document on your screen, type your address on the far left of the label....like this....
4. Next, in your layers pallet, add a blank layer and make sure it's highlighted by clicking on it.
5. Now, grab your Marquee tool by clicking on the little icon I have the arrow by.....make sure the box I've circled in red labeled Feather has a 0 in it. Unless of course you want the little box we're going to put around the return address to have rounded corners. If you want rounded corners put a higher number in. I kept mine square.

6. Once you have your marquee too, draw a box around your return
address. You will see a dotted line that's moving....it's called
marching ants....don't ask....I don't know.
7. Now go to EDIT>STROKE and the dialogue box [pictured below]
will appear. In the box labeled width put 1 if you want your border to
look like mine....a higher number if you want it thicker.
Color:
If you like the color shown proceed, but if you want another color,
double click on the color shown and you can pick another one. I chose
green to go with my theme.
Location: Outside
Blending: Normal
Opacity: 100% .....just like the box above shows.
8. Now you should have a border around your return address.....just like mine :)
9. Go over to the right and type in the address you are sending your letter/card to. You may want to make type this in a bigger font than the return address so the post office doesn't get confused. Mine is bigger, but could be even a little bigger, I think.
10. Now make another blank layer and grab your paint brush and a color[s] you like or some nice scrapbooking elements you have on hand....any kind of graphics will do....and make it pretty...


11. If you want a border around the whole design, like mine, you can add one more blank layer on top of all your other layers and repeat steps 5-7.....just make the border thicker by typing in a larger number in the "Width" box.
12. Print it out....place it on your envelope to get the fold right....get the glue out and voila.....
12. HAVE FUN!