Thanks to some very kind friends with lots of sample jars at hand and well-priced blogsales, I was able to get a whole slew of new pale/pale-ish foundations to swatch! I did thick swatches with about as much product as I'd use to make up my full face to try and show off the undertones and depth of each product. Bear in mind that I haven't tried most of these products on my face yet, and some foundations blend out lighter or darker on one's face than they do in a swatch.
FROM LEFT TO RIGHT: Armani Lasting Silk foundation in #2 Ivory, Dolce & Gabbana Luminous Liquid foundation in 60 Classic, Flower About Face foundation in LF1, Becca Luminous Skin Color in Sand, Becca Radiant Skin Satin Finish foundation in Shell, Ellis Faas Skin Veil in S101, Illamasqua Skin Base in 2
Based on these swatches and what I've seen in person and in the photos (and just that--the D&G is the only one I've worn!), the D&G liquid and Illamasqua skin base are the lightest and closest to MAC N5-10, followed by the Flower foundation and Becca RSSF, which appear to be about MAC N10-15. The Armani appears to be the darkest, probably around N15-20, followed by Becca LSC, although LSC is notorious for being very sheer and malleable. The Ellis Faas is quite peachy. After washing my hands with soap twice, Skin Base and Lasting Silk were still visible on my skin.