Many designers selling their patterns on Ravelry have committed to donating some or all of their proceeds to relief organizations in Haiti.

A complete list of the patterns tagged 'Help for Haiti' can be found here. Using the 'Patterns' tab at this link, you can look up patterns that are in your queue or that you have favorited. This might be a good time to buy that pattern you've had your eye on for a while or something you know that you will be making some day.

At the advice of the yarn harlot, I'm putting up the knit signal for Haiti. The symbol is in recognition of the fact that knitters are a force to be reckoned with when we put our minds to something. Today, whether you are a knitter or not, do what you can for the people of Haiti.

You can donate to Doctors Without Borders here. Quoted from the Yarn Harlot's blog:

The MSF Hospital has sustained damage that means it isn't functioning as a hospital right now. Staff have moved to the courtyard
and set up tents and what materials they could retrieve from the
building and are doing their best to help people as they can. Doctors
who were providing maternity care are now running a trauma centre.

They, and their sister offices in other countries spent all night figuring out who could go and how to get them there, and staff is packing as we read this to get there as fast as they can. They'll be taking inflatable surgery suites with them so they can use that instead of their damaged buildings.

There are directed donation sites set up for Haiti on all of their websites, but I'd like to take a moment to ask you to please make your donation "undirected". Money given to a specific fund can only be used for that area and making sure your donation is undirected helps them a lot. It lets them keep serving other crises that continue to happen while the world watches Haiti, and more importantly, it allows them to be first responders.

On their websites (Canada here, USA here,here)
when you give there is a drop-down menu that you'll see called "I would
like my gift to be directed to..." and you'll see a lot of choices.
Please consider selecting "Greatest Needs" or "Emergency Relief" so
that they can have the flexibility that they need to do their best
work. Other countries can find their site

You can also donate to the Red Cross here.
The easiest way to donate is to text the word 'Haiti' to '90999' and
$10 will be billed on your next cell phone bill by the Red Cross.

The US State Department website links to this list of many different (valid) charities which are directing funds to Haiti.