Most likely you’ve seen cell phone “short codes” when advertisers on sandwich wrappers or big media brands like American Idol create text message-based voting campaigns. You know, text a message to this 5 or so digit mobile code and get some free stuff you don’t really want. But more smaller organizations and communities are turning to short codes with the help of startups.

Do you need one? If you want to market or promote something to mobile users, manage mobile communications to members of a group or organization, or get cell phone users to access your mobile application or service — then, maybe. How much are you willing to spend and what kind do you need? Here is some things to know about short codes, how to get them and what to avoid:

There are two kinds of short codes, shared and dedicated. Dedicated short codes are dedicated for one customer, and are costly and take awhile to set up – in the U.S. it can cost anywhere from $15,000 to $30,000 per year and take two months to get it ready.

Shared short codes are shared among customers and use keywords to identify their traffic. The cost of these is pretty small, and you can access these services from companies like Mozes and TextMarks. Mozes has been actively signing up bands while TextMarks has been working on organizations and local communities.

If you want to obtain a dedicated short code in the U.S., you have to choose between vanity or select (hand-picked) and random codes. It’s like picking a license plate. Vanity codes cost around $1,000 per month just to register and random short codes cost about half that.

Registration of dedicated short codes is only part of the process if you want your own code. You’ll probably want to go to one of the dozen or so SMS aggregator companies that have relationships with different carriers like Clickatell, or VeriSign. Research all the prices and compare as they are all trying to undercut each other.

If you are a content provider you can’t have to much fun either. According to the CTIA site you generally have to: “Agree not to transmit political marketing (news is acceptable), religious, pornographic, prostitution/escort, gambling, hate, alcohol or drug related content.” Wonder how FAITH and PLBOY (see below) are working that out.

A huge plus, If you text HELP or STOP to a short code, the service should respond. This is implemented to help users end or learn more about the short code service, and is useful for managing and finding these services.

Here are some sms shot codes, some did not respond to help/stop: COKE, 20FOX, FAITH, FBOOK (Facebook), GAWK (Gawker Media), MYSPC, (MySpace) PLBOY (PlayBoy).