Over the past few months I've been working on three new directory sites, which are all hosted on Lunarpages.
These sites are <sites removed -- no longer Lunarpages hosted>.
The thing most other webmasters ask me (or anyone with a directory site I suppose) is "where do you get the data?"
For the gardening site I did initially look at some data that could be purchased. Perhaps I wasn't looking at a data from a good source, but many of the listings seemed to be mis-categorized (example: florists as garden centers), often out of date (many missing or bad URLs), and missing large geograpical areas (the West coast had very thin data from what I saw).
So, I get the data the hard way - by doing many searches online using varying search engines, and then looking over the websites I find to see if a business should be included. While this does take absolutely forever (I have no idea when I'll finish my vegan site), I'm happy with the quality and uniqueness of my data. The real flaw in this system is that my sites tend to be weak in iconic local establishments that don't have web sites.