Save the Date
The Tory accountability report must be tabled the week of September 28th, with a Liberal opposition day to follow 2 sitting days later (Sept 30 to Oct 6). This parliament could also meet its maker if the Tories introduce a ways and means motion around that time - which would probably be the way they'd like to go down, since Harper could then go around yapping about how the opposition parties voted against the home renovation tax credit (only, he'll probably phrase it as "the Liberal-socialist-separatist coalition killed the home reno tax credit"). Now, the Conservatives could bring in the ways and means motion 2 weeks earlier but that would nix Obama-Harper photo ops, so I can't see that happening.
So, if you're planning a "non-confidence party", I'd start booking bars for late September or early October.
With a 36 day campaign minimum, that sets us up for a November 9th or November 16th election.