Make sure you have the pertinent Thiele-Small parameters for the particular driver you want to use, or get them for several you are interested in.
Then download WinISD at
http://www.linearteam.dk/ -- this is an easy program to use to model woofer cabs; just insert the name of a speaker and its Thiele-Small parameters and it will pull up a few graphs. Then you can experiment with different box tunings and INTERNAL sizes.
Read the Help files to learn about "group delay" and response curves so that you truly understand all the trade-offs involved; ported cabinets have the direct frontal output, and the delayed output of the frequencies that the port handles -- this as a general rule induces more delay the lower you go, and is the reason why some people talk about smeared response or mushiness.
The best designs are those that fit your circumstances (are you using a low B, what type of tone are you after, which comprimises do you feel are the best for you, etc).
Have fun. I've done quite a few, often sounding better than a manufacturer's using the same driver. And this beats doing all the calculations with formulas on paper by a long shot.