Unfortunately it's currently not an easy thing to do, to go back and forth from cash to bitcoin. I still haven't figured out a good way either, only that the reason it seems to be so hard is because our governments have all these laws and regulations designed to keep us from easily doing this.
They don't seem to want us exchanging all of our old state & country backed currencies into any of these new and innovative online crypto currencies, which are not backed by war and governments but instead by the people who love, develop and support them.
So there's no great answer to this right now, but the typical responses would be circle.com, coinbase, localbitcoins, and libertyx, and those will work as long as you can meet all of their strict requirements.
answered Jul 20 '15 at 5:59