How do you keep up with your to-do list? Is it on paper? In your email account? As long as your system works, it’s a good one.

I have used a combination of tools to help me keep my to-do list in order. Most of the time it works pretty well.

Between visual cues (items left on the desk or by the door to remind me), items in my GMail Inbox (I send emails to myself a lot), and an online to-do list for repeating tasks, my bases are pretty well covered.

As for the online tools, I have found a couple of websites to be especially useful. For the past year, I’ve been a user of RememberTheMilk. It’s a versatile site that allows the user to organize their to-do lists in a number of ways. The free version of the site is feature packed, but if you want any integration with a smartphone (I’m on an iPhone, myself), you’ll have to annie-up for the Pro version, at the tune of $25/year.

When my RememberTheMilk account came up for renewal this year, I chose to let it expire and go looking for another tool with similar features. A quick post on Twitter yielded some great feedback. Thanks to Jason Heydasch, I learned about Toodledo.

The free version of Toodledo has as many (probably even more) features than RememberTheMilk’s Pro version. The Toodledo iPhone app is only $2.99, a considerable amount less than the yearly fees at RememberTheMilk.

One of the most useful features of Toodledo is the ability to seperate tasks by context. I work out of at least two different offices during any given week, so this feature makes it easy for me to see only the tasks that are relevant to my focus at the time.

At first glance the interface of Toodledo might seem overwhelming and slightly rugged. But take a few minutes to look over the introduction and explanation of features. I quickly picked up the interface after I understood a little more about how it worked. It’s actually quite intuitive, highly customizable and versatile.

In my opinion, Toodledo is one of the best to-do management applications available, with a feature set that will work for most anyone, smartphone integration at a reasonable cost, and lots of plugins and widgets to help you keep track wherever you are online.