Try this for a start.
Mobilehomeparkstore.com and loopnet.com are the most widely used websites to find mobile home parks. I am a big advocate of the direct mail method as I have bought about 75% of my deals this way. You will also want to attend national events where you can network with other investors all over the country. I have bought 3 deals in the last 18 months this way. The Mobile Home Millions conference in Anaheim, CA would be a great opportunity to network and potentially find some good deals out there.
You can purchase owner data from MHparkstore.com. You can also contact your title company (usually you have to request the report from the customer service department) and ask them to run a customer report based upon the criteria that you are requesting, i.e. all mobile home parks in a certain zip code, county, or state. If you gather the information using the 2nd method, make sure and look at the tax value to try and determine how big the park is.
There is also another website called MHVillage.com that has really good information about mobile home parks (including pictures). It costs $7 per park in order to gain all of the information about the park.