I've added a little more data to the F1 2011 Year in Review spreadsheet, so here's a quick R script to generate a chart showing how the teams progressed during qualifying.
The following chart shows a loess model over the fastest times recorded by both drivers in the team during qualifying by each team over the 2011 season (so in constructing the model, there are two data points per team for each race):
This chart shows a loess model over the fastest time recorded within each team over all qualifying sessions:
Here's how they were created:
See also: F1 2011 Review - Another Look at Fastest Laptime Evolution