Some of the options when you cannot make Roth contributions, in my best plain english:
1. If you have a retirement plan at work that allows you you to make contributions directly out of your salary before taxes are calculated, you can make contributions unless you are already contributing the maximum allowed in your plan at work.
2. You can make contributions to a "traditional" IRA. If you or your spouse have access to a retirement plan through work, your traditional IRA contribution may not be tax deductible based on a phase out similar to the Roth, but you can still make non-deductible contributions. In a traditional IRA you only pay taxes when you take the money out (the withdrawal is considered income in the year you take it), but you do not pay taxes at withdrawal on a prorated portion based on money you have already paid tax on (the non-deductible contributions). If either you or your spouse has access to a retirement plan at work and are not eligible to contribute to a Roth IRA, you likely would not be able deduct your traditional IRA contributions. Current laws would allow you to convert a traditional IRA to a Roth IRA after 2009 with out the income limitations.
3. You can also save into an account that has no tax deferral such as a plain old brokerage account. Some people advocate buying non-income producing securities so they don't have to pay annual income tax and then holding them to pay the lower long-term capital gains rates in the future when they finally sell them. This is possible, but in practice it is harder to do than it sounds.
There are a number of other places to save money into but these are the most common for saving for retirement when you can't contribute to the Roth IRA.
On the issue of contributing to the Roth and then learning you've made too much money in the same year, Nickel addresses "Recharacterization" well in the http://www.fivecentnickel.com/2007/01/1 ... -mistakes/
link. The only thing I'll add, in the spirit of plain english, a Recharacterization is done by getting a "Recharacterization" form from the company where you keep your IRA account, filling it out, and returning it to them before the tax filing deadline. If you don't have a traditional IRA, you will need to open one so the recharacterized money can go into it.