We recently built a cool site called This R That for a client.
Besides having a great UI that my son, Zach, built, it also has a neat architecture for a Twitter search site. The major weakness of the Twitter search API is that rate limiting is based on the IP making the request. While Twitter won’t reveal the actual limit, it is believed to be about 200 an hour. If you build a web page that takes the search request and sends it to a server to do the work, that server’s IP will be capped at the rate limit across all users. A popular site would reach that limit fast.