Each year the SWL section of the VERON organizes the SLP Competition for SWL's on the HF amateur bands. SLP stands for "Short Listening Period". The competition consists of 8 separate contests spread over the year and are planned in the weekends of major international HAM contests, so that at least reasonable activity on the HF bands can be guaranteed.
The SWL section of the Dutch Radioamateur Association, VERON, organizes several SWL contests throughout the year. Each year starting with the "SWL New Year Contest" on the first Sunday of January.
Then the "SLP Contests" (Short Listening Period): 8 times, the first in the last full weekend of January en the 8th in the last full weekend of October.
Each SLP has a winner and the 8 contests together form a competition with an overall winner.
Finally there is the "28MHz SWL Contest" in the second full weekend of December, simultaneous with the ARRL 10M Contest. For the details, such as the contest rules and the results: http://swl.veron.nl/swlcontest.htm .
The Straight Key Century Club (SKCC) has added a SWL category to its monthly CW contest. The next "sprint" occurs this weekend starting at 0000 UTC on July 12th (Saturday evening 2000 EDT US). It lasts 24 hours.