selling / producing a script

1. Enter screenplay competitions. I recommend NICHOLL - do a search.
They wont produce your script, but if it stands out, can lead to things including an agent.

2. Have a staged reading of the script with temporary actors before an audience of potential investors, directors, producers.

Hello lwyneck,
I suggest you read a few of the many books on how to sell SPs. You will find them in any Border's, etc. Entering SP competition, as GREATwarEAGLE suggested, is a great first start. Also, look for up-and-coming production companies that are developing projects in your same topic and contact them asking whether they will be willing to read your SP. - MAKE SURE YOU REGISTER IT! with the US copyright office and the AWG BEFORE you show your SP to anyone.

Finally, if you have some money to invest, get the SP covered by a respected script editing/coverage service. There are dozens of excellent editors online that will provide you with coverage for less than $200.
Check: http://www.scripts-and-coverage.com/screenplays/coverage-services.asp

Selling or optioning a SP is the dream of thousands of writers. It is a difficult and extremely competitive process. So don't get discouraged! Keep your day job and keep fighting for your SP. Most writers spend years moving a project around until they finally hit the jackpot.
Best Wishes!.