Linux - APT

I wish I could get a count of how many times I've used these commands, forgotten them, and had to google them again. 


(show what version of package is installed)
dpkg -s collectd-core
  blah blah blah
  Version: 5.4.0-2ppa1

(uninstall package)
sudo apt-get remove collectd-core

(show versions available for the package)
apt-cache showpkg collectd-core
  blah blah blah
  Provides:
  5.4.0-2ppa1 -
  5.2.0-2ubuntu1 -
  4.10.1-2.1ubuntu7 -

(install a specific version)
sudo apt-get install collectd-core=5.2.0-2ubuntu1

(show where the various package versions are coming from)
apt-cache madison collectd-core
  collectd-core | 5.4.0-2ppa1 | http://something.com/junk/ precise/main amd64 Packages
  collectd-core | 5.2.0-2ubuntu1 | http://barf.com/apt/ precise/main amd64 Packages
  collectd-core | 4.10.1-2.1ubuntu7 | http://trash.com/ubuntu/ precise/universe amd64 Packages





(show where your box is configured to pull packages from)
/etc/apt# cat sources.list
  ###### Ubuntu Main Repos
  blah blah
  ###### Ubuntu Update Repos
  blah blah