I tried google but couldn't find exactly what I was looking for. Is there any site (such as ticketmaster, but perhaps more invasive..) that lists theatrical/concerts in Paris?

The French Tourist office gave me a list of everything going on in Paris in October. See if you can get this info on their web site.

Never mind..I don't see it on the site. Call them and have them fax you the list for the month you are interested in.

There are always the websites for specific theaters, of course (ie, the Opera houses, Theatre des Champs-Elysees, Casino de Paris, etc. There are definitely Freench ticket agency websites, also, which will be somewhat limited by their arrangements (some venues only list with one) and will only have somewhat major events. www.ticketnet.fr is one of them, as well as www.fnac.com

FNAC is a music/book/electronics store but also has a ticket agency. Their addon fees are not really very much, so it's a good site to buy them.

If you want a comprehensive list of every concert in Paris, even the very cheap or free ones in Paris, it's not readily available. The Tourist Office website used to be the best for that (they had an events section and did list most everything), but they've redesigned their website and now I think they don't have a lot of the minor ones any more, and you can't easily just list them by date and genre. You can check, though. www.parisinfo.com then go to "what's on"

In practicality, you don't need to plan in advance much for the minor ones, though, so it doesn't matter so much. I just get an entertainment guide when I arrive (Pariscope, etc.) and plan from there. I only buy advance tickets for the major venues (Opera Garnier, etc.)

Here you go:
http://whatsonwhen.com/pages/paris.jml