Writing assistance systems, from simple spelling checkers to more complex grammar and readability analyzers, can be helpful aids to nonnative writers of English. However, many writing assistance systems have two disadvantages. First, they are not designed to encourage skills learning and independence in their users; instead, users may begin to use the system as a crutch. Second, they use a "one-size-fits-all" approach, treating all writers' problems as equivalent. In this paper we describe TechWriter, a personalizable writing assistance program for advanced learners of English that encourages skills learning. We describe TechWriter's basic writing assistance functionalities, how it can be used by writers alone and working together with writing tutors, who it can be personalized for, and how it can help writers acquire better writing skills over time. (Contains 3 figures, 2 tables and 3 notes.)