It happens all the time: you type a URL into your browser address bar, hit enter, and there's a long pause before anything happens. The delay might be down to the remote site. It may be because your ISP is busy. But another possibility is that your DNS server (the computer that translates a domain like www.google.com into an IP address like 188.8.131.52) is just slow. DNS lookups normally take a fraction of a second, but slow servers might take 3, 4, 5 seconds or more to return any information for some sites, and that can quickly become very frustrating.
You don't have to use the DNS server provided by your ISP, though. There are plenty of public alternatives around, and namebench can help you find out whether any of these would improve your surfing speeds.
To get started, launch the program and choose your most commonly used browser in the Benchmark Data Source list. Click "Start Benchmark" and namebench will extract 200 recent URLs from your browser history, then query several DNS servers for each one.
You should stop using your PC while the benchmark is running, just to ensure that you don't skew the results. Go make a coffee or something, give the program the 10 or 15 minutes it needs, then come back and admire the finished report: detailed charts and graphs that tell you exactly how fast each server is, and recommend the two that you need to use.
You'll still have to change your DNS server settings manually, unfortunately. Not sure how? Then view this Google page, replacing its server IP addresses with the ones that namebench recommends.