And the amount: 247.5 billion ISK. This figure comes from the Icelandic Financial Services Association in their comment on the new government's 10-step plan of general debt relief to Icelandic households (they don't really comment on it, they are going to wait until the government actually describes how they're going to do this).
What are the sources and the reason for the debt relief so far? The IFSA comment has a handy table to show us (my translation). The left-most column is mine as I thought it would be informative to note where the initiative for each part came from. In the cases of where I've put "Legal System" it is due to rulings regarding the illegality of certain credit contracts, first and foremost ISK denominated debt that is indexed to the exchange rate. That sort of indexation is illegal in Iceland since 2001 (though it did not stop the contracts to be created during the height of the credit party). Finally, do note that the figures due to ruling 600/2012 (a supreme court ruling regarding the illegality of certain exchange-rate indexed loans) are estimates and not entirely realised as of yet.
The total debt relief to Icelandic households, 2009-3Q2012.
Despite this nearly 250 billion ISK relief, Icelandic households are still pretty indebted. In the newest Financial Stability report, the Central Bank of Iceland estimated that the outstanding household debt amounted to around 110% of GDP. That is roughly the same ballpark as Ireland is playing in - although the Irish are not paying a 4-5% real rate of interest on their debt as Icelanders do.
From the newest Financial Stability Report (Central Bank of Iceland)
Nevertheless, the debt jubilee has of course had some effects; one should expect that when debt amounting to 15% of GDP is cancelled. But the situation is still fragile and we should not expect it to improve as easily as it did in the early 2000s when an investment boom was creating a lot of jobs and wage income.
Icelandic households' ability to live on after-tax monthly income (source: Statistics Iceland)