A few days ago, I had two appointments downtown in the financial district on the same day. I wasn't sure how close they were to each other, so I got the idea to look them up on google maps. However, I soon found out that you cannot plot more than one location on google maps at a time. (Well, that's not completely true, since you could plot one point, and then get directions from there to the other place. But then what would you do if you needed to plot three places?)
So, I decided to see if I could hack something together using the Google Maps API. The result is at: http://gmaps.kaeding.name
It isn't pretty, nor is it perfect, but hey, it works (at least when the addresses are accepted by the geocoder).
You enter as many addresses as you want, one per line. Then the script sends those strings through geocoder.us to get latitude and longitude. (The Google Maps API only allows you to plot points using latitude and longitude, not by supplying an address). Sometimes, geocoder.us will come back with more than one possible address for a single string. So, the next page asks you to confirm the addresses. The final page displays the map.