According to Anthony McCann, there are 13 types. This is a big deal because, he explains,
"The choice of appropriations form has two significant impacts. First, it can create very real problem in budget execution. Second, many of these forms move away from the traditional fixed annual appropriation by which Congress has historically implemented the “power of the purse.” As such they subtly change the balance between the executive and legislative branches and markedly reduce Congress’ ability to control spending."
Tony's "Forms of Appropriation: A Typology," appeared in Public Budgeting and Finance and is at http://onlinelibrary.wiley.com/doi/10.1111/pbaf.12096/abstract (pay wall). Congressional staff likely can acquire a copy via request to the Library of Congress or Congressional Research Service.
McCann, by the way, formerly served as Clerk and Staff Director of the subcommittee of the House Appropriations Committee, and has extensive public finance experience. Presently he lectures at the University of Maryland's School of Public Policy.