Helping people with computers... one answer at a time.
Slow Domain Name System (DNS) lookups can affect your apparent internet speed. Your ISP should provide fast DNS, but there are also alternatives.
My ISP's DNS servers are timing out frequently, what can I do?
DNS, or Domain Name System, is what turns an internet name like www.yahoo.com into an internet address, such as 126.96.36.199. In essence it's an enormous distributed database. If you're interested in more gory details, HowStuffWorks has a good overview here.
Your ISP provides servers that perform the DNS lookup function each time you access a name on the internet. Sometimes those servers can have problems which range from not knowing the names they should, to taking a long time to perform the lookup.
So I'll be clear: once you've determined that you have a DNS problem, your first step should be to complain to your ISP. You and all their other customers will benefit if they address their problem.
Unfortunately, some ISPs don't seem to care much about the little guy. They make it difficult to report problems and seem to do everything possible to avoid taking responsibility. I've been there, and I switched ISPs as a result. If you're not getting satisfaction from your ISP I strongly suggest you vote with your feet.
However I realize that switching ISPs can be painful, and it's not always a practical option. So I do have a couple of alternatives.
AnalogX FastCache is a caching DNS server for Windows that runs on your local machine and handles the DNS requests that your computer makes. The first time you ask for a name, it goes to your ISP's DNS Servers to get the address. After that every time you ask for the same names again it gives it to you instantly. A friend in the industry recommends it highly. Even with a good ISP things seem to run a little snappier with FastCache installed.
Another alternative is to simply use a DNS provided by someone other than your ISP. This can get a little risky as unlike your ISP, whomever you choose will have no responsibility for keeping you working. Some possibilities include:
Simply use the DNS servers of a different ISP. Rather than publish IP addresses here, just ask someone you know for the DNS they're running with and see if they work for you.
Use the DNS Servers provided by OpenDNS. (This is what I've been using lately.)
Another approach may be to use the Internet's root DNS servers directly. These are a set of 13 DNS Servers that are by definition the master copies of the DNS database. Remember though, that you'll be competing with thousands of other DNS Servers who also use the root servers as their reference point.
Many people report good results using the "unofficial" Open Root Confederation DNS Servers.