Agricultural census records are probably one of the most interesting records one can find for their ancestors. I like them so much that a few years back I intended to release a series of transcriptions and indexes for the records from a variety of counties that my ancestors lived in between 1850 and 1880. Those big plans were essentially scrapped, though at some point I will release what I had been working on. I believe these records are (or should be) going to show up on a site like Ancestry or Footnote long before I could finish my project, so I'll just make this quick and painless.
The first ag census I looked at was from 1850 in St. Charles County, Missouri. The index has been done for some time now; I actually printed this out and gave a copy to the St. Charles County Genealogical Society. This is something I've been wanting to put online and now is the time.
Index to the 1850 Agricultural Census of St. Charles County, Missouri