Bored of the relatively plain default plymouth theme that Ubuntu ships with? You can easily sass it up with more themes – like this one, called ‘ubuntu sunrise, by dinin over on Gnome-look.
The theme can be found on GNOME-Look where a.deb file is provided for pain-free installation.
NOTE: If your current Plymouth theme is garbled you may want to follow Softpedia’s ‘fix’ @ http://news.softpedia.com/news/How-to-Fix-the-Big-and-Ugly-Plymouth-Logo-in-Ubuntu-10-04-140810.shtml (thanks Niels!)