For those that don't know, Radegast is a lightweight client for Second Life. While it doesn't have the full capabilities of the full viewer (or 3rd party viewers like Firestorm or Singularity), it also doesn't tax your system like those others. You can do IMs, group chat, teleporting, moving, give/accept inventory, search, area search, voice, text-to-speech (for accessibility) and there's a very simple 3D viewer. You can also view HUDs and interact with them.
I use Radegast on my baby laptop (which has very limited graphics capability) and whenever I need the resources on my desktop such as running Photoshop.
Radegast is also popular among people who play Tiny Empires in Second Life since it allows you to have many "alts" logged in at one time - again without slogging your system.
Anyway, it's been a long spell between updates on Radegast but Latif Khalifa, the developer, came out with an one last week. While it had some nifty new features in it, there were a few significant bugs that got unearthed as it went into wider use. Today, Latif came out with v2.16 and so far it seems solid.
If you already use Radegast, this is a recommended update. If you have never tried it, you should.
Latif also works on Singularity too.