Housed at the Indiana State Library, this index covers up through 1850. Wildcards are not used, but partial names can be entered, which serves the same purpose. Searching for Wil New is advised when searching for a name such as William Newman.
Soundex is not supported, so be clever with those names and keep in mind alternate spellings.
The searches can be conducted with only one letter in each box--at least when this tip was written. That's really neat as most sites do not allow that.
The database is located here http://126.96.36.199/INMarriages1850/marriages_search.asp