Farming for Blockheads adds a Seed Market to Minecraft, similar to the Market from Pam's Harvestcraft, but with a search bar and a scrolling grid. It is compatible with all of Pam's Seeds and Saplings and can be configured further to add new trades. There are plans for more things in this mod - think Cooking for Blockheads, but related to Farming.
While it supports Pam's Harvestcraft, it does not require it in order to run. The plan is to support other farming mods as they come up.