Charlie Lane
Mentioning the Unmentionables: Underwear During the Regency

In preparation for a particular steamy scene in Keep No Secrets, I researched Regency underwear. Fun Times! Here are the sources I found most useful:
Mary Shelley and getting dressed during the Regency
This short video not only goes through the layers a woman would wear during the Regency, but it also (oddly, in my opinion) relates the events of the celebrated house party where Mary Shelley first conceived of Frankenstein. So if you have an interest in that, come for the clothing and stay for the peek into a major literary historical moment.
The Great Underwear Debate by Donna Hatch
I love this article so much. Informative AND entertaining. I love it when researchers pay attention to the subtle nuances in events and trends.
ThreadingThroughTime on Pantalettes
SUCH a good source on how pantalettes were constructed, what they look like, and what difficulties ladies may have had while wearing them.
Risky Regencies Keeps it Risque
This source confirms much of what the other sources does but adds additional information about women wearing drawers in Italy!