2-row ranges from about 34-37 ppg and 2-3 Lovibond. Extra Light and Pilsener DME will be the closest extracts when compared to pure 2-row or pure Pilsener Malt. I don't use LME since DME has a better shelf life, lighter color, easier to measure, and you get more bang for your buck with it.
Extra Light and Pilsener DME ranges from about 37-44 ppg and is 2-5 Lovibond. Light DME values are a bit higher than this, which is why I don't use it. Amber and Dark DME are out of the question for partial mashers because 1) either you don't know what specific ingredients or proportions they contain, or 2) you're already mashing with those grains inherent in the extract.
Extract, in general, will often contain a portion of Carapils and/or Light crystal. It's not usually pure 2-row. Since the ppg in extract is often a little higher, it's difficult for extract brewers (and sometimes partial mash brewers) to attain low FG's. Therefore, if you want a dry PM or Extract beer, it is recommended to substitute about 8-12% of extract with fully fermentable sugar (sucrose or glucose) and to make a big, healthy starter with high attenuating yeast.
Use hopville.com to build a recipe via beercalculus. Get the ppg/L right by choosing specific brands and ensuring the purported numbers are accurate by double checking the value on the maltsters website. For example: Briess Golden Light DME is 43 ppg/5 L whereas Muntons Extra Light Dry Malt Extract is 37 ppg/3 L. Just because you see preset values in there doesn't mean they are accurate. For example: Gambrinus Honey Malt has an incorrect default ppg in hopville. It's more like 35, not 27.