As an alternative...

"...I used my trusty Modge Podge..."
As an alternative to decoupage products I have started to use the faux finishing glaze that you add to paint for wall techniques.

Some advantages are:
1) you can buy it by the quart/gallon for about $12/$25 versus $8-10 for 8oz. of Modge Podge.
2) over time decoupage products can turn yellow and I haven't had that happen with the glaze.
3) it is thinner and easier to spread, which is especially nice for large projects. It goes farther.

Some disadvantages are:
1) is thinner and easier to spread, which can be a pain for very small paper projects.
2) there can be some color transfer so make sure you don't work out of the original container. This is especially true when working with printer inks or tissue paper.

Don't get me wrong, I also love Modge Podge, but I wanted to share my experience with an alternative just to let everyone know that there was something else out there. As with many good discoveries this one was born of necessity for large amounts of inexepensive product! You can also ask your paint retailer to tint the glaze to achieve certain effects such as brown for aging (tea stained look) or white for sun-bleaching. I have even heard of people using tinted glaze to change the look of existing wallpaper just so they can live with it for awhile longer!