For some reason, when I get onto a client's network and run /sbin/dhclient on my hacked-together-linux notebook, dhclient gets an IP address via DHCP, but doesn't update my /etc/resolv.conf with the local name servers, so names don't get resolved using DNS.

I haven't figured out a fix for this yet, but a temporary work-around is to have a look at the lease in the /var/state/dhcp/dhclient.leases file. You should see a line like "option domain-name-servers 192.168.94.49;". Just put that IP address in the /etc/resolv.conf file (ie "nameserver 192.168.94.49").