I'm in Viet Nam and most social websites (Facebook, Twitter and the likes - even reddit) are blocked by the ISP DNS server.
I tried to change the DNS server of my Arch box using the resolv.conf file, but it failed miserably since dhcpd generates this file automatically everytime I connect to the LAN. I've been looking around to try and find out how to fix this, without success. Either I s*ck at Googling, either it is non-trivial to do so.
EDIT 1:
Meh, apparently posting it here made me feel guilty and I had to push my search a bit more. I found the same article than Ankur post below. This is what I made, if anybody ever faces the same problem:
$ sudo gvim /etc/dhcpcd.conf
Add "nohook resolv.conf" at the tail of the file.
$ sudo gvim /etc/resolv.conf
Add to the file (OpenDNS servers):
nameserver 208.67.222.222
nameserver 208.67.220.220
Or (Google DNS):
nameserver 8.8.8.8
nameserver 8.8.4.4
Then, verify it worked (need package dnsutils):
$ dig www.facebook.com
; <<>> DiG 9.9.1-P1 <<>> www.facebook.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16994
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;www.facebook.com. IN A
;; ANSWER SECTION:
www.facebook.com. 89 IN A 69.171.224.53
;; Query time: 87 msec
;; SERVER: 208.67.222.222#53(208.67.222.222)
;; WHEN: Thu Jun 28 00:43:23 2012
;; MSG SIZE rcvd: 61
See ;; SERVER: 208.67.222.222#53(208.67.222.222), it worked.