There are a number of Sri Lankan recipe sites. The ones below are recommended.
Asia Recipe.Com. Not a lot of recipes but what's there is good and I like the glossary of Indian ingredients giving English equivalents
Malini's Kitchen. A terrific contributor driven recipe site.
My Sri Lanka. Online site for chef Peter Kuravita's SBS television program in Australia.
Sarogini's Sri Lanka Food.net. A small set of good recipes from this Perth, Australia, based cook.
Sri Lanka: The Miracle. Freelance Larry Austin's site for all things Sri Lankan including recipes and restaurants in Sri Lanka.