Lithuania has this clause written right in the constitution (Article 68): 50,000 citizens of the Republic of Lithuania who have the electoral right may submit a draft law to the Seimas and the Seimas must consider it. (Seimas being the parliament)
Currently there's this new wave of citizen initiatives, including websites promoting government expenditure and transparency, blogs (one is actually called 50000.lt after the constitutional article), petition sites, a website which lets you look up your representative and fire him an email right away, and another, which provides an API to monitor parliament resolutions and voting statistics. But combining the petition sites with real electronic signatures to actually enforce the 68th article, now that's a novel idea. There are already bank logins with two factor authentication. And we've had these European ID cards with biometric data which work as a passport in the Schengen area, and each of these cards have a digital certificate on a chip inside, which can be used for electronic document signing (with a government-based certificate authority) so all that's left right now is to combine the two.
Thank you Slashdot for the idea! I'm off to gather some coders and start changing the world.