Burlap is a very popular medium right now, and quite appropriate for fall decor. You could wrap the vase with either burlap fabric or ribbon, then tie it up with some raffia. Or go for the "trash and treasure" theme and tie it up with some bright red satin. Burlap is cheap and the process is easy.

Also, you could purchase some bamboo sticks, and then line them up and tie them around the outside of the vase.

Wrapping with newspaper and tying with strips of a plastic bag or 6-pack rings would create a very unique conversation piece and highlight a recycling theme. But this might not be appropriate depending upon what your party theme is.

Wow, sarosen, it looks like you didn't get timely help for your question, although sheri posted some good ideas. What did you end up doing after all? I've encountered this problem myself a few different times...

Tack 2000 is a great spray glue by Design Master-- you can get it in some craft stores. By spraying a light coat around the vase, you can cover the vase with Spanish Moss & tie with twine, or cover it with fabric pretty easily. I have even used spray paint to coat the INSIDE of clear glass vases. Metallic gold & silver work nicely, and look good through the glass. You might want to try it sometime with a cheap vase you don't like. I prefer Design master brand because it dries really fast.