See this this Op-Ed over at the New York Times. The writer has what seems to be a pretty good idea. He says the government could help out most by reducing interest rates and making it easier for people to buy homes or refinance mortgages. That would in turn slow the massive slide in housing prices. Here is a quote:
The government is in a great position to cut rates by about a point: Through Fannie Mae, Freddie Mac and the Federal Housing Administration, it now controls nearly 90 percent of all mortgage originations. These lower rates would apply to most home buyers who take out a loan under $729,750 for a house that they will live in.
Along with lower rates, the government should provide temporary down-payment assistance for buyers. The government could, for example, match the amount of money that buyers use for a down payment, up to $15,000. Because the government now controls the bulk of all mortgage financing, this money could be provided directly at closing. Homeowners who refinance their current mortgages could also receive assistance, allowing them to avoid foreclosure.
Programs like these would draw buyers into the housing market and reduce the backlog of unsold and vacant homes. Investors and speculators would be ineligible and would face the full cost of their mistakes.
By stabilizing house prices, these programs would benefit the bulk of Americans, who own a home but did not get involved in the subprime mortgage market. Price stability would more directly achieve the goals of the Wall Street bailout: increase the value of mortgage-backed securities (by increasing the value of the underlying houses) while injecting government capital into the financial system.