Diodon is a lightweight clipboard manager for Linux written in Vala which "aims to be the best integrated clipboard manager for the Gnome/GTK+ desktop". It doesn't have as many features as Glippy, Pastie and so on but it's a lot lighter and only uses around 2.7 mb of RAM on my system.
Diodon features include Ubuntu indicator, clipboard sync (primary selection and Ctrl+C / Ctrl+V clipboard) and an option to set the clipboard size.
Install Diodon clipboard manager in Ubuntu
Diodon comes with two PPAs: stable and daily builds. To add the stable PPA and install Diodon in Ubuntu 10.10 Maverick Meerkat (the PPA doesn't have packages for other Ubuntu versions), use the following commands:
sudo add-apt-repository ppa:diodon-team/stable sudo apt-get update sudo apt-get install diodon
If you like bleeding-edge software, you can find the daily builds PPA HERE.
Diodon is very new so you may find bugs; report them @ Launchpad.
Thanks to Garry for the tip!