# dpkg -l | grep dbgsym
ii firefox-3.0-dbgsym 3.0.3+nobinonly-0ubuntu2 debug symbols for package firefox-3.0
ii libnss3-1d-dbgsym 3.12.0.3-0ubuntu5 debug symbols for package libnss3-1d
ii xulrunner-1.9-dbgsym 1.9.0.3+nobinonly-0ubuntu1 debug symbols for package xulrunner-1.9
FWIW (on my system):
# dpkg -l | grep dbgsym -0ubuntu2 debug symbols for package firefox-3.0 1.9-dbgsym 1.9.0.3+ nobinonly- 0ubuntu1 debug symbols for package xulrunner-1.9
ii firefox-3.0-dbgsym 3.0.3+nobinonly
ii libnss3-1d-dbgsym 3.12.0.3-0ubuntu5 debug symbols for package libnss3-1d
ii xulrunner-