Generally, horticulturists divide Nepenthes into two groups (or three, if you count intermediates) when discussing their cultivation depending on the elevation they are found at: highland species and lowland species. Highland species are from elevations of 1000 meters or more above sea level, and lowland species are found less than 1000 meters from sea level. However, it is important to note that these categories are only general and are even arbitrary in many cases - a large number of species have populations that straddle the 1000m mark (which are generally called intermediates), or separate populations that occur both above and below the line. Like always, the most important consideration when growing these plants is to know the habitat and preferences of the exact species (or species form) you have!
The most crucial difference between the cultivation of lowland and highland plants is their preferred daytime and nighttime temperatures, although there are other aspects to consider as well. For that reason, we've split our Nepenthes grow guide into separate categories for lowland plants and highland plants.
This altitudinal chart is a great overall guide of the elevations where many Nepenthes species are found. I've been told that there are some inaccuracies and missing information on it, but in general it's a good resource to keep in mind.
I was also recently alerted to Tom Bennet's interactive chart here. It's a very thorough resource and also features a hybrid calculator.