The government is in a unique position to influence the economy through its actions. Nudging the interest rate nudges the economy. Large tax and spending changes create more substantial impact. These are essential functions.
During the Bush years, the government went into debt to give money to taxpayers at the expense of the overall community and at a time when the economy did not need the stimulation. This contributed significantly to turning an ordinary real estate downturn into an economic meltdown.*
During the last decade, money flowed up to the rich as both tax breaks and big bonuses. When worthless investments disappeared from the economy, jobs and a substantial portion of the nation's wealth disappeared as well. The proportion of wealth held by the rich increased, and money at the poor end started drying up completely. This inequality is bad for the majority of citizens and bad per se for the health of the economy.
Use the power of government to continue to send money to the bottom 90% of the economy now. Unemployment insurance. Public works jobs. Payment for previously volunteer jobs. Open up poverty programs like food stamps to those with minimal incomes even if they have assets. We want to reward saving and preserve the assets of the bottom 90%, not force them to sell off their retirement.
Investing bubbles in real estate derivatives, dotcom startups, and junk bonds have been responsible for the last few recessions. One common thread among these is too much risk for the entire market to bear. There needs to be a mechanism to limit the quantity of high-risk investments in the market.
Another related common thread is investing in speculation rather than in growth. Investing in companies contributes to economic growth. Speculating on which way prices will go skims money off the economy and hurts long-term growth investment. Thus, it should not be treated the same as growth investment. Speculation investment should be limited and burdened with a surcharge. This is not as cut and dried as I have made it sound. For example, you can use foreign currency as a hedge against foreign stocks to eliminate currency risk. This should not be surcharged. Or you can speculate in foreign currency on its own, and this should be surcharged. The professionals have the knowledge to sort it out.
High-frequency traders have been gaming the market with bazillions of bids and asks. Easy solution for this is a ha'penny tax on each bid and ask whether or not it goes through. Long-term traders won't notice the difference because they (should) trade infrequently.
Use taxation to get money back from the superwealthy.
Temporarily apply a high estate tax with a $1.5 million exemption
Charge a higher CG tax on speculation (derivatives, etc.) and disallow losses.
Introduce tiered CG tax for growth investments that ties in with income tax. If a retired person is living on $25K in investment income annually, he shouldn't be taxed the same as a person who has $25K investment income on top of a $2MM salary.
Mandatory retirement contribution from salary
Change tax laws so as not to penalize those who are withdrawing retirement funds to live on. Ideally, these people should not have to live on their IRAs or 401ks before retirement at all.
Add annual tax for those who own residential property but don't live in it.
Offer tax credits for landlords who are renting property on a rent-to-own basis. England has had a formal rent-to-own program for years.
Offer tax credits for bringing jobs into the US and for converting location-fixed US jobs to telecommuting US jobs. Telecommuting offers new employment opportunities for people in areas where jobs are scarce and allows them to stay in their homes (which are probably underwater).
*since this isn't about the causes of the meltdown, I'm only touching lightly here