e.g.
# find /var/log -type f -exec du -sm {} \; | sort -n -r | head -20
41 /var/log/cabal/WorldSvr_10_01.log 35 /var/log/cabal/DBAgent_10.log 34 /var/log/cabal/WorldSvr_10_10.log 5 /var/log/maillog.4 5 /var/log/maillog.3 5 /var/log/cabal/WorldSvr_10_05.log 5 /var/log/cabal/WorldSvr_10_04.log 5 /var/log/cabal/WorldSvr_10_02.log 4 /var/log/cabal/WorldSvr_10_03.log 4 /var/log/cabal/LoginSvr_01.log 3 /var/log/maillog.2 3 /var/log/maillog.1 1 /var/log/yum.log 1 /var/log/Xorg.0.log.old 1 /var/log/Xorg.0.log 1 /var/log/wtmp.1 1 /var/log/wtmp 1 /var/log/secure.4 1 /var/log/secure.3 1 /var/log/secure.2