UPDATE 14/09/10: As well as the Graphical clients there is the fantastic Radegast client, it's text based with a gui to move around, view maps, listen to music streams on land! also allows you to use a radar and interact with objects nearby all via a gui menu. No graphics but I find it fantastic for logging in for chat/gigs etc as it also allows me to run other software while logged in, highly recommended.
UPDATE 13/11/09: Boy Lane has just released a Netbook build of his Rainbow viewer, optimised for running on Atom based Netbooks. I've installed and tested and it runs VERY well, averaging 10fps wherever I went and no need for all the fiddly bits: Grab it here
Need to get SL/Opensim client up and running at a half decent rate? After playing around with a number of viewers and configs I think i've finally managed to get best out of it that I can (i'm using a EEEPC 901 and 2gb RAM).
What to expect: you won't be doing a lot of building with this but it does run with enough speed to login/communicate and to attend lectures/conferences - this is the main use for me when i'm away from my main pc to keep up to date.
Step 1: Download the neccessary files, first off is the older SL 1.19 viewer that does not have windlight and runs much better on older machines:
http://download-secondlife-com.s3.amazonaws.com/Second_Life_1-19-0-5_Setup.exe
Install this and make a note of the install directory (if you can, try and put it in the default install location).
Step 2: Download the latest Boy Lane Windows Cool Viewer release from here:
http://coolviewer.googlecode.com/files/CoolViewer_i686_1_19_0_5_Release_59_exe_xml_only.exe
Install this over the SL 1.19 viewer directory, it will automatically try and pull in the neccessary DLL's and such so no need to mess.
Step 3: Fire up the cool viewer and go to edit -> preferences and make the following changes:
Under the Graphics tab ensure it's set to run in a window at 800x600 (auto detect works well).
Set your draw distance to 64 - as low as it can be configured from here but we'll change that in a mo.
Under the Graphics detail tab set all the sliders to as low as they will go, Avatar rendering to normal, Lighting to sun and moon only and terrain detail to low.
Under the Adv graphics tab set Max Particle count to 0, outfit composite limit to 0.
Optionally: goto the audio and video tab and deselect streaming music and video then mute the master volume - this speeds up the fps a fair bit and is fine if your not using voice.
Step 4: Login to the grid and press CTRL+ALT+D to bring up the debug menu's.
Go to Client->More->Debug Settings and in the window type renderfarclip -> this should be set to 64 but change this to whatever you want, the lower the better. I've set mine to 16. This alters how far ahead of your avatar objects are rendered - in small enclosed spaces this makes no real difference to what you can see.
Nextup change the rendering options: Client->Rendering->Features
Turn off everything in here apart from the UI - this should add 5fps or so to the speed.
Next go to Client->Rendering types and turn off the following:
Alpha
Tree
Water
Grass
Clouds
Particles
Bump
Also if your attending a lecture etc then once your sat in place turn off character as well, this make a huge difference to FPS, in my case it adds 10 fps.
ok, thats all the settings i've found that needed changing, at the moment i'm walking around at 10-25 fps depending on where I am, it's also worth altering your AV, the less attachments and extra's the better. You can also go though the above steps on any other viewer to speed it up a bit.
Overall it looks OK - your not going to be going around taking in the vistas but in a classroom or conference situation it's perfect for communication and getting points across.
Hope this helps!
