Some of the warmest ones carried by Team Estrogen are (in no particular order):

No Excuses Cold Weather Run Tight by Craft
http://www.teamestrogen.com/prodCR_1901019.html

Select Thermal Tight by Pearl Izumi
http://www.teamestrogen.com/prodPI_12211021.html

AmFIB Tight by Pearl Izumi
http://www.teamestrogen.com/prodPI_4355.html

Oslo Tights by Louis Garneau
http://www.teamestrogen.com/prodLG_1060083.html

Firewall 220 Tight by Sugoi
http://www.teamestrogen.com/prodSU_40552F.html

SubZero Tight and SubZero Zap Tight by Sugoi
http://www.teamestrogen.com/prodSU_40401F.html
http://www.teamestrogen.com/prodSU_40462F.html

The SubZero is warmer than the MidZero

MidZero Tight and MidZero Zap Tight by Sugoi
http://www.teamestrogen.com/prodSU_40311F.html
http://www.teamestrogen.com/prodSU_40331F.html

Storm Tight by Craft
http://www.teamestrogen.com/prodCR_193363.html

Insulator Expert Tight by CW-X
http://www.teamestrogen.com/prodCW_120879.html

WeatherPro Tight by Shebeest
http://www.teamestrogen.com/prodSB_2902.html

For our winters here in Portland, I use the Sugoi MidZero Zap tight and for the coldest days, I wear a Craft longjohn style baselayer under them http://shop.craftsports.us/layer/bas...underpant.html (not carried by Team Estrogen). And wool socks.

Ride long and stay warm :-)
Edna