The recent addition of scripted REST APIs and API version support has really made working with ServiceNow integrations as easy and robust as they should be in this day of highly connected systems. Managing, supporting, and deprecating API versions can be a challenge if you don't have access to usage statistics. The Helsinki release take API management to a new level.
Since many of the projects I work on are integrations I'm frequently working with custom orchestration activities. Most of these also involve some sort of REST interface. The introduction of ServiceNow's REST Inspector was a huge help, but I wanted to introduce you to another tool I found extremely useful. It's RequestBin from Runscope.