For cheap vinyl check out
www.uscutter.com or signwarehouse.com
WHOA! I knew of USCutter.com and almost bought a vinyl cutter from them, but never looked into their vinyl supply section. I've always ordered from SignWarehouse.com because based on my research they had the best prices compared to most. But I'm now seeing that USCutter is less! Looks like by a few cents to $2.00 per item, but $9.99 flat rate shipping, and no tax (Signwarehouse does not charge tax outside of Texas) - any savings helps since things add up so my next order will be with them to try them out.
I order Oracal 651, and they have the application tape I use so I'll try that too. But I am noticing that SignWarehouse has more sizes, I often use 8 inch width rolls of both vinyl and application tape which I see USCutter does not have. But most of my work is with 15 inch rolls with USC does have.
Total cost for a roll of Gold from USC is: $15.49 , it's $17.50 at SignWarehouse. - OK so at this point I'm just kind of thinking out loud!
For anyone interested in upgrading to a larger vinyl cutting machine do your homework and research first. Very tempting to buy a generic Chinese brand cutter because their prices are a lot lower, but you may run into issues down the road - happened to me! If you want something for yourself that you will occasionally use, then a generic cutter will probably be ok. If you want to start a little business on the side or sell things on eBay or fleamarkets, you should invest in something more reliable and trusted.
Before buying any machine, you'll want to research its parts and accessories to see how much the replacements will be - everything from the cutting strip, pen/blade holder if you loose yours, and especially the cutting blades.
There's a great forum that constantly gets questions from beginners who are just starting out and are wondering what and where to buy, so there's plenty of information! :
There's two helpful sections -
Machine info:
http://www.t-shirtforums.com/vinyl-cutters-plotters-transfers/
Vinyl material, "how to" and "where to":
http://www.t-shirtforums.com/vinyl-signs-decals/
There's also different types of vinyl with different strengths and lifespans, so research that before ordering. I'm very chatty when it comes to vinyl and I did a ton of research before starting out and learned a lot along the way, so if anyone has any questions I'll be happy to try and help

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***** Oh and by the way. If you visit any website, and they are selling Oracal vinyl color charts - you can request the same chart for free from the Oracal website. This would be handy if you plan to order rolls of different colors often.