In the good tradition of my minimalistic, no frills, log information comes - Experiencelog.

It shows you when you've got experience points in a tab in your chat, how many points you've got, how many points you have and how many points you still need for advancement.

This addon supports the slash command:

/xplog <number>

where <number> is the number of the chat tab you want the output to be in.
In example:
/xplog 2
puts the output into the second tab of your chat window.
Default is the first tab.

Volunteer for French localization desired.