I'm surprised nobody has mentioned the San Jose, CA (Santana Row) Superchargers. One set is designated as public (in a multistory parking garage), the other is technically in a valet area (but as of the time I visited it, there wasn't anything preventing you from just driving up to the chargers and plugging in). They're less than 100 yards apart (horizontally anyway), but they count as separate sites on the Tesla Web site, in-car nav, and supercharge.info.
Bruce.
Bruce.