In this paper we describe briefly three systems: onCue a desktop internet-access toolbar, Snip!t a web-based bookmarking application and ontoPIM an ontology-based personal task-management system. These embody context issues to differing degrees, and we use them to exemplify more general issues concerning the use of contextual information in 'intelligent' interfaces. We look at issues relating to interaction and 'appropriate intelligence', at different types of context that arise and at architectural lessons we have learnt. We also highlight outstanding problems, in particular the need to computationally describe and communicate context where reasoning and inference is distributed.