if you're on windows...use nslookup:
START->RUN-> "cmd"
> nslookup -type=txt ._domainkey.domain.com
For example:
C:\Documents and Settings\joe>nslookup -type=txt gamma._domainkey.gmail.com
Server: ns1.xxxxx.org
Address: 10.200.200.5
Non-authoritative answer:
gamma._domainkey.gmail.com text =
"k=rsa; t=y; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDIhyR3oItOy22ZOaBrIVe9m/iME3RqOJeasANSpg2YTHTYV+Xtp4xwf5gTjCmHQEMOs0qYu0FYiNQPQogJ2t0Mfx9zNu06rfRBDjiIU9tpx2T+NGlWZ8
qhbiLo5By8apJavLyqTLavyPSrvsx0B3YzC63T4Age2CDqZYA+OwSMWQIDAQAB"
gmail.com nameserver = ns1.google.com
gmail.com nameserver = ns3.google.com
gmail.com nameserver = ns2.google.com
gmail.com nameserver = ns4.google.com
ns1.google.com internet address = 216.239.32.10
ns2.google.com internet address = 216.239.34.10
ns3.google.com internet address = 216.239.36.10