PDNSD is the solution for caching DNS, and easy way .
Very handy if you shut down your computer often or using dial-up to haven't to wait for dns resolve when you connect on the net.

Features:
# permanent disk cache (useful for frequent power-offs/reboots)
# usually smaller memory footprint (depends on cache size)
# offline-detection prevents hangs up
# better control about timeouts (also to prevent hangs)
# better control over the cache
# better run-time control
PDNS documentation

apt-get install pdnsd you get v1.1.11par-1 on the site the last version (pdnsd-1.2.1-par) but you 'll have to compile the source.
----------------------------------------
I've got a problem with download torrents and using Firefox for www, Azureus has proper limits and I left 10KB/s for my browsing
or radio on the net.
The problem is that Firefox don't respect the Azureus Bandwidth, for example if I Go a site flash loaded my torrent speed decay....

Searching on google, freshmeat and the dear knoppix forum The answers I found were very mid-level on linux, and for me the rookie,
read about ip tables , pools, and other things were very difficult to applicate only for one app (firefox).

But I found trickle which is easy, quick and direct...and better it works!!!
I tested downloading a file (14MB) and only use the 10KB/s I put as limit ... my torrents are safe

Trickle site The bonus! no compilation apt-get install tricke