It is a catastrophe. If you want to help by making a donation, think of trying:
Medecins Sans Frontiers / Doctors without Borders (This link gives you a list of links for online donations from various countries; note the US link at the bottom of the page.)
The Red Cross (Note that donations here go to a general relief fund; if you want to specify Haiti, you’ll need to mail it in.)
It is hard to tell whether funds in some cases will go into a general fund or will be dedicated to Haitian relief efforts.
From the US State Department:
To help, text “HAITI” to “90999″ and a donation of $10 will be given automatically to the Red Cross to help with relief efforts, charged to your cell phone bill. Or visit Red Cross and Mercy Corps to contribute. Also call 1-888-407-4747