localbitcoins, or google "bitcoin atm" they are in a lot of major cities now. You can even try posting a craigslist advertisement saying you are buying bitcoin for cash locally. It has worked for me in the past, just be careful when you meet up. Do it at a public place with free wifi, and be sure to get the coins before you hand over the cash.

If you really want to be as anonymous as possible with it, park down the road and walk to the meeting place (mcdonalds, starbucks etc.) or have a friend drive you. This is to avoid being identified by license plates. However if you aren't worried about anonymity it's much easier.