Important: The venue is not really reachable by foot from the airport, that is why I recommend to travel to Zaventem station and not to Zaventem airport!
Zaventem airport is right next to the venue. The area around the airport however is not very pedestrian friendly, the easiest way to get to a hotel closeby is to use a taxi or the shuttlebus of the hotel you're staying at. Zaventem airport has a train station right under the airport from where you can take a train into the city. Be aware that there's something called the "Diabolo tax" that's added onto any train journey that starts from the airport's train station. You can also take busses from the airport into town or to Zaventem main station.
Charleroi, the low cost airport is in Belgian measures pretty far from Brussels: it's about 44 km from the capitol. There are 2 ways you can get from Charleroi to Brussels that are explained on the following Wikipedia page (shuttlebus and train).
There are several high-speed connections from the capitols around Belgium to Brussel-Zuid, which is in the city center from where you can take the train to Zaventem station. You can get the train schedules at the website of the NMBS. Their website is a monster that will make you load 2 pages before it even considers giving you it's advice and that will eat up 2 mb of bandwith in the process. They also don't have referenceable url's and don't even allow you to link into their site or use their data (there used to be a third party iphone app that they shut down - yes that's our tax money).
The shuttle bus that takes people to the corporate village from Zaventem station or from Zaventem airport is not working on weekends. That leaves us with the following 3 options:
Got any other information you want to share? Leave a comment!