The Kokua Viewer team has Linux viewer out for Second Life™, at least a test version. It comes in both 32 and 64 bit versions, runs on Debian Stable, aka Jessie, and newer versions.
They need testers. See: KokuaNT is available for testing.

Second Life and Virtual Worlds
General Viewer Information
The Kokua Viewer team has Linux viewer out for Second Life™, at least a test version. It comes in both 32 and 64 bit versions, runs on Debian Stable, aka Jessie, and newer versions.
They need testers. See: KokuaNT is available for testing.

The third party Second Life™ viewer Dolphin Viewer is no longer updating. Lance has run out of RL time to work on it. The end was announced 2015/06/22. See: Good bye, and thanks for all the fish.

There have been a couple of updates to the Black Dragon Viewer since I started using 2.4.2.6. NiranV is up to release 2.4.3.1. The changes fix some minor problems, adds Windows 10 support (Win 10 coming the end of the month), and includes the change to how we can use clothing layers.

RLVa is still broken… but, that’s not a Black Dragon issue, if I remember correctly.
A new release of the Alchemy Viewer is out, Alchemy Beta 3.8.0. This not new news… I’m just catching up. There is not much one can say about what is new in Alchemy as they aren’t telling, deciding to let it be a surprise to users. Right.

The release notes read:
But, there are a number of Alchemy changes if you scroll down. One interesting one is the ability to export a group membership list to a CSV file. That could be useful. Exporting ban lists for use in other groups might be more useful. Also, added to the inventory panel filters is an option to filter LINKs, the basic entry used in the Outfits folder. Third party viewers allow LINKs to be created outside the Outfits folder. So, I can see a need to search for LINKs.
Tuesday (6/30) at about 11 AM PT the Lindens announced the partial release of Experience Tools. I write ‘partial’ because they are only fully released to Premium Members. This afternoon the 3.8.0 (302622) Jun 12 viewer automatically downloaded and I installed it.
This is also the main viewer now. Look at the download page.
That is a Jul 2, 2014 video.
The announcement is here: Experience Tools Available Now For Premium Members!
All users can get the viewer and use it. My understanding is only Premium Members can build experiences with this viewer, but all users can enjoy the experiences.
There is a knowledge Base article that helps you get started creating experiences. See: Experiences in Second Life. This is for both those wanting to participate in an experience and those wanting to create an experience.
There is a forum section the beta testers and early adopters used. It is now open to all. See: Experience Tools Forum.
You can find experiences to play in Second Life™ here; Resident-created experiences in our Destination Guide and the Linden Portal Parks.
I’ve been seeing slower rendering of scenes in Second Life™ for some time. It’s like taking 4 steps better-forward, 2 worse-back, 1 back, 1 forward… changing often with each viewer release. It is hard for me to tell if it is me/my-computer or actually the viewer changing. Now others are mentioning that things are taking a long time to render, which suggests it is more the viewer than it is me. Enough so that a developer asked at the Third Party Devs’ meeting if there had been any changes to the interest list processing that may have slowed things down.

Oz Linden answered there have been no deliberate changes to the interest list. He also points out that as complicated as the SL system is other changes could affect the interest list processing. So, Oz wants to hear about misbehaving render.