Super Sentai is essentially Japanese Power Rangers. Remember, from the 90s "Mighty Morphin Power Rangers". Well, those shows where remade versions of the Japanese series.
You might say, "What? Power Rangers are for kids!" Yes - they are, and so is Super Sentai. BUT - It's one heck of a kick-ass kids show. From what I can tell Super Sentai is much more respected in Japan - and is a big part of their pop culture.
See, Super Sentai has been on the air, unhalted, since 1975 with "Goranger". 33 different series later, and Sentai is still going strong. Why? Becuase it constantly re-invents it's self while also sticking to a formula. Some shows from Japan make different versions of themselves, which has helped make Sentai surprisingly refreshing. While one series might be a little more goofy and kid friendly like "Go-Onger" - another series like "Gekiranger" will take a more serious and stylish approch.
To help catch you up - the latest Super Sentai series are thus:
1.) Gekirangers (2007) A kung-fu masterpiece depicting rivaling factions of the martial art "Juken", taking on beast traits in fighting. Both the good guys and the bad guys are striving to become stronger.
2.) Go-Ongers (2008) A decidedly more kid friendly series, Go-Ongers features talking cars fighting against polluting villains. With a focus on a racing theme, the show is more fun and silly with charming results. Think of Pixar but done in Power Rangers style.
3.) Shinkengers (2009) The latest series featuring Samurai fighting to stop invading demons. Following the 18th Lord of the Shiba clan, the Shinkengers use Kanji based powers and origami robots.
There's a wide variety of Super Sentai, and I encourage anyone to take a look. Youtube has some good clips to teach anyone about the series. If you really liked the original Power Rangers, I suggest you look at "Zyuranger", which is where the footage for the show was taken from.
While Super Sentai isn't likely to come over to the US anytime soon, think of these series as an introduction to Japan, and something worth investigating yourself through the net.