There are lists of top places to visit for Halloween in SL and of course the SL Destination Guide also has tons of info. on sims, haunted houses, and all things Halloween related.
I thought I'd just put a few of my top Halloween sim picks here that I like to tell people about. Granted there are many fantastic haunted houses but these 4 are either full sim or much more than just a haunted house and all very worth a visit. Enjoy.
Valyria, Calas Galadhon, : http://maps.secondlife.com/secondlife/Lost%20Stars/128/128/39
Prevously blogged in more detail here: http://karasecondlife.blogspot.com/2015/10/calas-galahdons-valyria-2015-halloween.html
This one is by Truck Meredith and Tymus (Ty)Tenk. This is a must see for sure. Look at my past blog post or just go and enjoy. Be sure to ride the dragons, make it through the snow and to the huge event cavern which is the coolest thing and take the boat ride too.
Halloween Town by Laura Liberty here: http://maps.secondlife.com/secondlife/Townies/119/103/99
Super cute fun place.. another must see with added parts each year. Nice long fun haunted movie vignettes to play in and enjoy in a cute sim plus merchandise.
The Greatest Halloween Ride in the World Ever here: http://maps.secondlife.com/secondlife/ASD%20Studios/130/15/2006
This is a long wild ride.. the house pic doesn't do it justice on the inside. It is presented by Alicia Stella. Their sim info. says: "Come ride the Most amazing Halloween Experience in Second Life! 20 Rooms of Terror! Over 15 Minute theme park attraction. Unlike any Haunted House in Second Life! Halloween Freebies available. Updated for 2015 with several new rooms! Scary horror spook"
Caverns of Zyn here: http://maps.secondlife.com/secondlife/Aigle/45/30/1517
This boat canal ride by Zyndyrr through the caverns is really great in mouse look.