It's January, and I forgot to contribute to my IRA. Is it too late?
No. Generally speaking, the IRS allows you to make your IRA contribution for a particular tax year up until April 15 of the following year. This rule applies to both traditional IRAs and Roth IRAs, giving you some flexibility in terms of the timing of your annual IRA contribution. You can contribute a total of $5,500 to all the IRAs you own in 2015 (unchanged from 2014). In addition, if you're age 50 or older, you can make an extra "catch-up" contribution of $1,000 a year in 2014 and 2015.
Note that you can make your annual IRA contribution in a series of payments rather than in one lump sum. For example, let's say you want to invest the maximum amount in your IRA for 2015. You can either make a lump-sum contribution of $5,500, or you can set up a savings plan whereby you invest a fixed amount each month in your IRA. Because you're allowed to spread your 2015 IRA contribution over a 15½-month period (January 1, 2015 through April 15, 2016), you can invest as little as $354.83 per month and still end up contributing the full $5,500.