It still airs in the US on Nicktoons Network. And on Canal 5 (my favorite channel as a kid) and Nickelodeon in Mexico. We have been told it's airing everywhere in the world by fans but we don't really know which channels.
You can see all 26 full length episodes on TurboNick for free!
Itunes has the first 19 episodes and will hopefully post the last 7 soon.
As far as I know, you can find every single episode on the bit torrent sites out there but the quality is all over the place.
There's a DVD selling in Latin America called "Dia De Los Malos." I don't know if they'll ever make them for the US or any other market. Keep your fingers crossed.
There's a PS2 and a Nintendo DS games out there.
There's the big NICKTOONS book which has an El Tigre chapter (with lots of development designs) and a ton of art from all the other amazing Nick shows like Ren & Stimpy, Teenage Robot, Invader Zim, Avatar, Sponge Bob, Mighty B, etc...
And of course there's the McDonalds toys....
And I forgot (thanks Jack) about the T-Shirts we made for Nick.com...
Please let us know if it's airing in your country (thanks Romson from Russia)!