Shadow Lane - Suncoast Casino in Las Vegas, and costs about 250$ plus the cost of the hotel - which isn't that bad, and the weekend - Venders Faire and Saturday night Ball, are all worth it.
Florida Moonshine - I plan on attending their June Beach Bash party but the location of their parties is kept private and the details only given to accepted members so it's not really possible to post them here.
www.floridamoonshine.com
Crimson Moon - I've never been but I know they are sort of a sister group of Florida Moonshine. They do have a website as well and you need to apply
http://www.chicagocrimsonmoon.com/
BU and TASSP are ones I've not attended and don't know much about.
Also, there are two east coast groups SCONY and NES, as well as TES which is a BDSM oriented group. SCONY I personally wouldn't recommend but NES is an excellent group - North Eastern Spankos. They hold very small parties, tight knit, invite only because they don't want it to grow too big. There is also another group called Dom Sub Friends which like TES has events all over the city.
TES and DSF have events at Paddles Club which usually holds their own spanking events as well - OTK Nights which take place the first Saturday of every month
There is a Nor Cal Birthday Party every three months as well where they celebrate the birthdays from the last three months. The next one is in February.
Hope that helps
Kate