Commissioning a museum computer exhibit can be a confusing business. This page has links to documents written by a range of experts. At the moment a lot of this advice is from people I know. But if you know of some other good advice on the web let me know and I'll add a link.
Home page of the Tate Modern handheld computer tour. Explains the system, gives you a taster and some of the evaluation and research done during its development. A great resource and an example other institutions should follow.
John Benfield is New Media Manager at the Natural History Museum in London. He's written a set of guidelines for making museum kiosks accessible.
Gail Durbin describes the how the V & A museum in London used computer exhibits to facilitate learning. This paper goes through the whole process from analysis of visitors' needs, different types of exhibit and surveys on their effectiveness.