Take a look at Big Daikon but don't stop there. It has been known for, shall we say, bellyaching at times.
JET will pay you better than the big language schools and treat you better. The hours are more reasonable and you won't have to work on weekends and holidays. But conditions vary across the board. You might get put in a school working 40 hours a week teaching 5 classes a day or you might get stuck the back aide of nowhere and teach 6 classes a week with very little to do in between. With the big language schools you can transfer, while on JET you can only transfer if you have a really, really good reason (need to be closer to medical care, got married and want to live with your spouse etc.) Being bored doesn't count, nor does just not getting along with coworkers.
You can only work for three years on JET, though extensions are possible in some cases and you need a 4 year degree. The process to get a JET job is long and not very fun at all, but when you put it on your resume it carries with it an amount of prestige for those who know about the program. Strictly hearsay, and it varies by region, but the success rate is something like 1 in 7.
You can PM me if you want to go into more detail. Please have some questions ready if you do - there is a character limit in PM -M