The Planetary Society maintains a complete, open dataset that tracks NASA’s annual finances requests, congressional appropriations, and remaining obligated expenditures from fiscal 12 months (FY) 1959 to the current.
It’s up to date twice every year, after the discharge of the Presidential Funds Request (PBR) and after passage of congressional appropriations.
These information and associated charts are free to make use of below the Creative Commons BY 4.0 license.