Some administrative and other helpful information is here, for those involved in developing OpenFormula:
Formula_Work shows who is working on what (past and present)
Test_Suite_Generator points to and explains that tool
Spreadsheet_Bugs lists some known bugs in existing applications, we'll want to test for many of them.
The formula subcommittee doesn't directly use this Wiki to develop the formula specification. Instead, it updates an OpenDocument document. You can download the latest draft, read the mailing list archive, and see other information at: http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=office-formula
If you are looking for general research data about spreadsheet formulas and functions, this external to OASIS site may be a good place to start: http://www.openformula.org/Research_Data