This D3 project is unfortunately no longer functional due to a change in Twitter's API. When I have more available time, I'll look into seeing whether it can be repurposed.
Twitter Map takes the latest geocoded tweets for a given search query and plots them on an Albers projection of the US. The map and tweet circles are drawn using D3.js while the contents tooltip uses a forked version of Tipsy. New tweets are plotted every 25 seconds.
Only about 1% of tweets are geocoded as the feature is opt-in, so only a small number of tweets processed are plotted. Limiting the geocoded tweets to a portion of North America reduces the set to an even smaller group. All of the filtering is done client-side, so this means a lot of tweets are returned but few actually appear on the map.
The Tipsy fork for SVG does not currently support IE, so the map is best viewed in Chrome, Firefox, Safari, or Opera. Look for the full blog post on this project in the near future.
Searching too frequently results in Twitter rate-limiting your IP for a limited amount of time. Rate-limiting is done to prevent abuse from runaway scripts, but it can be triggered here because so many GET requests are made in order to populate the map with a sufficient amount of tweets. Do not query repeatedly. I put in a quick fix to disable the form for 12 seconds after each new query to prevent this.