The Ontario Township Papers are miscellaneous land related papers filed by township, concession and lot. You never know what you’re going to find until you look. Sometimes there’s nothing interesting in the file, and at other times, you will find a petition from a settler requesting the Crown to bring over their relatives from such and such place in Ireland.
I have often found land matters listing people whom I didn’t know existed because they were gone by the censuses. This and the prospect of finding a potential place of origin in Ireland always keep me coming back.
These are on microfilm at the Family History Library where they can be found in the catalog under “Township Papers, ca. 1783-1870s.” The microfilm collection and the Archives of Ontario has accompanying articles directing you through this record collection: http://ao.minisisinc.com/scripts/mwimain.dll/144/ARCH_DESC_FACT/FACTSDESC/REFD+RG+1-58?SESSIONSEARCH
The key into this collection is to get the township, concession and lot for the property your ancestor was living on or granted. When you have identified this through the grant indexes (such as the Ontario Land Records Index) or a land deed, then make sure you have a map of the township, and search the surrounding lots and concessions bordering the property. I never do a rural Ontario case without looking at the Township Papers.