One thing is the surge in UK Independence Party support, and from the types of constituencies they "won" in May, there seem to be various strands of support.
The first one is what we can call the Maggie-Tony-Nigel voters. Seats which fell to Labour in the May 1997 landslide, have returned to the Conservatives and in May were won by UKIP. The impression here is that these were areas where the Conservatives did well when Margaret Thatcher was Prime Minister, and were won over by Tony Blair when he became leader of the Labour Party, becoming key in Labour winning the 1997 general election, and stuck with him in June 2001. By the May 2005 election, Blair had become jaded and tired, and these voters were losing faith in him, half-heartedly turning back to the Conservatives, while waiting for something else to come along. One thing that is striking is just how fickle these sorts of seats are - the Conservatives could lose their 2005 and 2010 seats easily.
The second one is the rural Tories. Another striking feature are true-blue rural areas falling to UKIP. Whether this is due to the Conservatives being seen as more urbanised, or for another reason (UKIP's stance on HS2?), I cannot be sure.
The third one is the radical Western Liberals. Even as early as the May 1999 European elections, it was clear that UKIP were doing well in parts of South West England which had Liberal Democrat MPs. And this has accelerated. If you want your politics to be slightly anti-establishment, you're not likely to vote for a party that is in Government.
The fourth one is the Northern Old Labour. What is noticeable is that UKIP topped the poll in seats which stuck with Labour through its lowest point - the June 1983 general election. Why abandon Labour now? Well, consider where Labour was ideologically in 1983 - one of its major policies at the time was to withdraw from the European Communities (the collective term for what were then the European Coal & Steel Community, the European Atomic Energy Community and the European Economic Community). And there was still quite a socially conservative strand reflecting general working-class values. Labour is now socially liberal and pro-EU, and for these voters UKIP offers them the Labour Party from an earlier era.
I appreciate these are quite broad generalisations, but the impression I get is that UKIP has been drawing its support from these different groups.