No hotkey (AFAIK) and a bit clunky to do, but . . . you open up negotiations with a civ ("We wish to propose a deal"). At the bottom of the "table" where the offered agreements / deal items get placed, there are three links : Clear Table -- New -- Active." It defaults to "New." Click on "Active" -- this shows you the currently active deals between you and this civ. If there is a number in parentheses, it indicates the number of turns remaining in the deal (example: "(7)Right of Passage" means a Right of Passage agreement has 7 more turns to go until it may be canceled honorably). If there is no parenthetical number, then it is an active deal, but may be canceled by either party (by clicking on the deal - which dumps you back to the "New" deal screen for renegotiation).
Try browsing through the Frequently Asked Questions thread (always one of the five or six top-most threads on the board) for answers to many questions like this.