From the University of Minnesota Extension:
1. Slice tomatoes into at least 1/2-inch slices. Put slices on a cookie sheet and freeze for 2 hours. Remove slices and put them into freezer bags or containers.
2. Slice tomatoes into at least 1/2-inch slices. Package in a rigid airtight container and fast freeze.
3. Wash tomatoes. Dip whole tomatoes in boiling water for 30 seconds to loosen skins. Core and peel. Freeze whole or in pieces. Pack into containers, leaving one inch of space at top. Seal and freeze.
