gfmessage - a gtk2 based onscreen message displayer
There are many powerful alternatives for the old good xmessage, but they all lack, as far as I can see, an important feature: They can't print formatted text. With gfmessage you can use any font, color or size to print your text in a popup window. You can use format options in the command line, but alternatively you can also use a markup language to format your message. Here you find more information about this:
Download here:
http://prdownload.berlios.de/gfmessage/gfmessage-0.1.tar.gz