This apron is made from a damask tablecloth and an embroidered fabric placemat.
Since the tablecloth is designed to be spilled on, this should be a pretty stain-resistant apron!
Why wear aprons? You mean besides the fact that I always splash or spill when cooking? And that I feel more feminine and domestic when wearing a pretty one? Read through my favorite-ever story about aprons: Apron Evangelism, from Hillbilly Housewife.
Other cheap sources of fabric can include new or used tablecloths you already have or from thrift stores (cut around any stains), sheets, curtain panels. I've used all of these to make dresses before, too. Make sure the drape of the fabric is what you want on your finished product. A crisp sateen sheet will give a much different look than a silky damask tablecloth or satin sheet.
For 50 free apron patterns, see here; it's also listed on my Favorite Resources page, 2/3 the way down, under "sewing".
Just think of the possibilities!