Various IRA notesSee the Self-directed IRA page for information on self-directed IRAs.
Interesting article on Investing in Real Estate in your 401k. I assume most of these considerations also apply to IRAs.
There are a variety of IRAs available (and not all of them are for retirement! e.g. the Educational IRA). In the Economic Growth and Tax Relief Reconciliation Act of 2001(EGTRRA), Congress greatly expanded the ways you can save money and save taxes.
People with a modest income can have Uncle Sam fund part of their retirement with the Saver's Credit. Self-employed folks can sock away up to 100% of their self-employment income in a Uni-K which is like a small 401(k) plan. Combining these two (reduce your AGI with the Uni-K to the point where Uncle Sam will contribute more to your retirement) will give you even more leverage.
You have until April 15th of the year after the tax year to open and fund your IRA. You can put in up to the lesser of your earned income or $2000($3000 for 2002-2004, $4000 for 2005-2007, $5000 from 2008 on) as long as your AGI is less than $95,000 for singles.
I recommend that folks get a Roth IRA, especially if they are currently in a low(or 0%) tax bracket. That will avoid the most taxes. If one of the following links is to a specific type of account, they are to Roth IRA pages.