Collaborative pianists usually have to make a repertoire list at some point in their life, either as a student or as a professional. It is just like making a CV/resume: the accumulation of information is easy - making it look good is challenging. The most crucial aspects of a repertoire list are organizing and formatting. Organization ensures that specific info can be found quickly, while formatting keeps the document's length under 19 pages.
Understandably, a beginning collaborative pianist may simply have their repertoire divided in to Vocal and Instrumental sections. A more experienced pianist with a larger repertoire list needs more than two categories, however. What many pianists do is arrange their vocal music repertoire into smaller categories of art song, opera, and musical theatre sections, and arrange their instrumental music by instrument or instrument family (brass, winds, strings). Using italics and bold fonts can be visually helpful when used to specify composer or show title. Other formatting tip: pianists with larger repertoire should avoid single columns, as they lead to epic sized lists. Double columns utilize space more efficiently.
Sometimes it helps to see what other pianists do to their lists. Here are one page samples of what I like to do with my formatting: Art Song, Opera and Operetta, Musical Theatre, and Instrumental. Also, I found more examples of how pianists can present repertoire lists, picked totally at random off of a Google Search: Amanda Johnston (click on repertoire), Casey Robards.