There are good places and there are great places. The places below have continually received good feedback from the teachers who work there. Salaries vary from place to place, but expect to get about 6 to 10 USD an hour. Be sure to ask about taxes as well. If you have to pay taxes, they're 15 to 30% of your salary. Ask how often you'll get paid, as well. The majority of places pay once a month, so you're going to have to plan and budget carefully.

Top Insitutes
English Life
PARI Cooperation
World Communication
Morton Taylor
Business Links
Multilingua
Fulbright
Camelot

More Tips
Be aware that some places ask for recibios de honorarios. If you can't get these, see if you can find someone who can lend you theirs. Remember to ask the institute if they require these or not before you start to work for them. Some of these offer off-site classes, meaning that you have to travel to a company or house to teach the classes. Some institutes offer a bit extra if you have off-site courses, other don't. You'll want to find out before accepting an off-site course.

I recommend emailing them your CV and then also going in person with your CV and personally asking for an interview. That way you can also see what the institute is like and if you would like teaching there. You'll also get to see what books they use. In addition, you can meet current teachers and see what they have to say about working at the institute.

Sharon de Hinojosa (naturegirl321) has lived and worked (mainly teaching English) in the US, Scotland, Spain, the Czech Republic, China, Korea, and Peru. As well as teaching short-term in Venezuela and Taiwan.

She has created The LA Job List http://www.thelajoblist.blogspot.com which lists schools, institutes and universities in 19 Latin American countries which offer English teaching positions.

Since living in Peru since August 2006, she wrote The Ultimate Peru List http://www.theultimateperulist.blogspot.com With 60 pages it's a comprehensive guide for those living in or moving to Peru.