I would like to be able to measure my rooms's frequency response across the spectrum to maximize speaker placement, rooms treatments, etc.

I dont have to have perfection, but I would love to be able to see the response and tweak. Is there cost effective software or tools that will let me do this?

I wouldnt want to spend more than $200- $300 tops, if that.

I am computer saavy if that is required.

I use and like this free software. Room EQ Wizard. It is intended to help set up an equalizer, but works well for measuring room response.
http://www.hometheatershack.com/roomeq/

It is well supported in at least two forums, including here.

Many use it with the radio shack spl meter. The RS meter does not do a good job at the higher frequency range, but there are as you will read, better but slightly more expensive expensive mic options. You will need a sound card with a line level input and you are good to go.

Great! That seems to be just what I need. I will dive into the specifics of it as soon as I can.

Do you know offhand if there is a mic input option in the $100 range or so?

Great! That seems to be just what I need. I will dive into the specifics of it as soon as I can.

Do you know offhand if there is a mic input option in the $100 range or so?

I think that the Behringer ECM8000 is often suggested. But check the forums for the latest thinking.

The Behringer ECM8000 mic is a very good mic. But it does require a mic pre-amp with phantom power.