Duxhetude,
Not to be a jerk, but his name is Buxtehude. He wrote mainly for organ.
Some big names composed for the Virginal in the late Renaissance and early Baroque periods. A quick Google search will give you more names, but here are a couple that come to mind that haven't been mentioned: Gibbons, Giovanni Picchi, Samuel Scheidt, John Bull.
Phillip Glass wrote a concerto for Harpsichord (I hate it). Also Poulenc, de Falla, and Martinu all wrote concertos. Even Ligeti wrote some works he intended for solo harpsichord. They're really unique.
Sweelinck, as mentioned, is great. He heavily influenced Bach. If you look through the toccatas that Sweelinck wrote, you'll notice they are incredibly similar to Bach's, but he simply expanded on the form.