Interactive maps are bandwidth heavy and in order for them to appear quickly on a website, a dedicated, fast hosting environment is required. MapBox is a hosting platform for interactive maps, and is an alternative to Google Maps. Created by Development Seed, MapBox offers a range of hosting deals - that includes a free deal for maps that will receive less than 3000 views / month. MapBox works in conjunction with TileMill - another DevSeed tool that lets users create interactive maps. Most recently, MapBox has linked its maps with Open Street Map data to provide street level detail.
MapBox has good documentation that takes users through the process of creating interactive maps. However, Development Seed offers map creation services and for mapping projects with good budgets ($20K plus), it's worth talking to them about what's possible.
All of Development Seed's tools are open source, and the same applies to the MapBox server code (theoretically, you can install MapBox on your own server, and host your own maps). Creating simple interactive maps and hosting them on MapBox is relatively simple and the documentation is clear - however, doing something more complex requires a certain level of technical skill.
Sam de Silva was involved in the Nai's Journalist Violations site - http://data.nai.org.af - Internews' first use of Development Seed and their tools. Development Seed has made numberous presentations at Internews HQ and has connections with a number of staff. Also, they participated in the Pakinstan Innovation Lab, which lead to the PakReport team utilising DevSeed's tools.