While ServiceNow doesn't come with a standards based REST API, it does provide a API that can be leveraged by REST based libaries and clients. The current ServiceNow REST API is available through the "JSON Web Service" plugin and is documented on the wiki. Last year I created a tool to show how to POST information to ServiceNow through the REST API.
I have just updated the tool to show HTTP components of the post as well as to show specific code samples in a variety of languages based on the REST query you make through the tool.
Read more at: ServiceNow REST API Tool
