In some areas, the concept is unfamiliar. For instance, I understand that in Michigan land contracts are pretty common. But in other areas of the country, people are more familiar with lease-options or lease-purchases. They're not precisely the same as land contracts, but they serve the same basic function for both buyer and seller.
However, as with lease-options, lease-purchases, wrap mortgages, contract for deed, and similar techniques, very few will be listed on the MLS. You (or your agent) often have to go out and make it happen. I've posted repeatedly on how to find lease-options; the same techniques are used to find (or develop) land contracts.
As for the dreaded "due on sale clause" mentioned by Cicely, it's true that any of the techniques I mentioned can trigger the due on sale clause. However, for a number of reasons it's unlikely to. The main reason is that, right now, lenders are delighted if someone's paying their mortgage on time. The last thing they need or want is to foreclose on a performing mortgage. There are also ways to minimize your risks with land contracts. Or you can eliminate the risk by using a land trust, properly structured. See http://www.landtrust.net for more information on land trusts.
Hope that helps.