I like the Fairfield inn & Suites, Bluebird Lane, Millville- Newer hotel, clean, breakfast included. I have also stayed at the Quality Inn & Suites, 1701 N. Second St., Millville- older hotel, still pretty decent, breakfast included.
Others I haven't stayed at but hear good things are the Holiday Inn Express in Vineland and the Country Inn in Millville.
There are also the VIP Suites in the Thunderbolt paddock.
There are definitely some to avoid, like the Days Inn, Econo Lodge, and the NJ Motor sports Inn.