Not Ready For Prime Time (Fandoms), or otherwise known as Not Prime Time, is a gen, het, femslash, and slash multifandom secret fiction exchange for medium sized fandoms, including any RPF fandoms with under 20,000 fics.

2015 schedule
April 19 to 30 - Sign ups
May 3 - Assignments go out by the latest
May 5 - Madness collection and prompts open
July 3 - Stories due
July 11 - Main collection goes live
July 12 - Madness collection goes live
July 16 - Author reveals

Sign ups are happening now until April 30th. There are many Yuletide fandoms that are eligible for NPT, so definitely take a look at the tag set.

Useful links:
The sign up form along with the sign up summary to see what people have requested/offered and how to sign up.
2015 tag set
Dear Prime Time Player letters on LJ | on DW (optional)
Frequently Asked Questions