GUI for watching logs (tail and grep)

I've discovered glogg, which describes itself as:

glogg is a multi-platform GUI application to browse and search through long or complex log files. It is designed with programmers and system administrators in mind. glogg can be seen as a graphical, interactive combination of grep and less.

It will also tail files if you enable the Follow File option.

Just search Ubuntu's Software Center!

Installation through command line:

sudo apt-get install glogg

Multitail is what you searching for:

it has tons of features. look here for some screenshots.

Also have a look at this question over there at serverfault.com

Some options are: Swatch and KSystemLog

There's a log viewer built into Ubuntu, which can also open any log file, called System Log.