There is a useful round-up over at Politicalbetting of the performance of the three main parties in the local by-elections held since the General Election (there have been over 100).
Although local elections are subject to numerous factors that in isolation can produce some unexpected results, such a large number of elections gives a useful barometer of public opinion. They also provide an opportunity to test whether political polls are providing an accurate picture of the health of support for the government and opposition parties.
So, what's the picture? Well, since the election the Tories have received an average of 29% of the vote, down 8% on the 37% share they received in local elections back in May. Their coalition partners, meanwhile, are fairing equally badly. The Liberal Democrats' average vote share has been 14% - down from 22% in May. Prety poor for a party accustomed in recent years for a growing share of the vote at local level.
Labour, meanwhile, have received an average 33% of the vote. This is up 6% on their May share of 27%. Not a barnstorming performance, but a respectable one for a party that so recently lost power.
There is, incidentally, a blog dedicated to recording (in forensic detail) the results of local by-elections - Britain Votes.