In the continued absence of any full-scale Scottish polling, arguably the most meaningful guide to the state of play is the Scottish subsamples of YouGov's GB-wide polls - the reason being that YouGov are the only firm that claims to weight their Scottish samples separately. (And, indeed, the figures they produce tend to be more stable than other firms.) The third post-election YouGov poll has now been released, and the Scottish subsample has the SNP narrowly ahead: SNP 33%, Labour 29%, Conservatives 27%, Liberal Democrats 7%, UKIP 2%, BNP 2%.
Of course, even properly-weighted subsamples have extremely high margins of error, but that problem can be reduced by looking at an average of all three YouGov subsamples since June 8th, which produces the following figures: SNP 33.3%, Labour 32.0%, Conservatives 25.7%, Liberal Democrats 5.7%.
That confirms the general impression of subsamples from across the polling industry, ie. that it's a very tight three-way battle, but that the SNP are probably just about still in the lead, Labour have probably moved up to second place, and the Tories have probably slipped back to third. There have now been thirteen Scottish subsamples from various firms since the election - eight have put the SNP ahead, four have put Labour ahead, and only one has put the Tories in front.