Data obtained from CapGeek.*
A public Google spreadsheet containing this cap info and the charts these visualizations are based upon is available here.
*This project is currently operating with a salary cap of $69.5 million for the 2014-'15 season, which is about halfway between the $71.1 million that was suggested in December, 2013 (and currently used in CapGeek's cap calculations) and a more recent (March 5. 2014) projected minimum of $68 milion. For this reason, available cap space will differ between CapGeek and the numbers protrayed here and in the public spreadsheet.