At times like this there's unfortunately always scams that start up trying to take advantage of people's generosity, so please tread carefully. It's best to donate via an organization who's already involved in sending aid or gain your information about where to make a donation from reputable sources like national newspaper or national tv stations websites.
World Vision for example has a "donate now" button right on their homepage that's for the cyclone victims and have been quoted by sites like CNN as being there. Whether they take PayPal I don't know, but I'd bet if you asked them to find a way you could donate, they'd have one. Maybe even PayPal has a way set up on their own site.