Check it out! Crafty Games has a ton of free Spycraft d20 stuff for download:
Classic Spycraft Downloads
This is essentially everything you need to play a spy & espionage version of the Modern d20 rules.
And speaking of Modern d20, there are a ton of free adventures over at WotC still available. And a few Web Enhancements.
Combine these with the Modern d20 SRD and the Future d20 SRD and you'll have enough gaming material to play a modern espionage based game for many years to come. And it's all FREE.
Also, be sure to grab this free d20 Modern bundle from RPGNow, too.