I am using the Intel 945G and was crashing a lot once I got to the "real" world (off the starter islands). Sometimes the crashes had more to do with the SL server than anything else. But there were some tweaks I had to do to get stablized. The information I found on the Internet was a pick and choose, test and tear my hair out, kind of experience. Hit and miss a lot of the time. I did finally piece together a configuration that worked best for ME.
One of the main things was setting my maximum bandwidth in SL (prefs: network) to slightly below the maximum upload (not download) speed of my ISP. In my case, using DSL, I set mine to 250. Setting it above the max UPLOAD speed of your ISP doesn't do a darned thing... other than congest your connection.
For ME... in the Intel graphics driver 3D settings, this worked best:
Asyn flip: off
Flipping policy: flip
Force S3TC Texture Compression: Off
FXT1 text compress: off
Driver mem footprint: normal
Text Color Depth: Desktop color depth
Anisotropic Filtering: Application Control
My basic display settings, 32 bit, 1024x768.
In SL I set my graphics to 800x600, fullscreen: 4-3. Under graphics detail I set no shaders, avatar rendering to normal, enable nearby local lights, and SOMETIMES I set terrain detail to High but usually leave it set to low. If I hit a really laggy area when I have it on, I turn it off. It helps A LOT.
In advanced graphics I selected 64MB for my graphics memory rather than the 128MB that my card has available. This stopped the issue that I was having with blue screen errors with the explaination that my driver got stuck in a infinite loop. I haven't had that error since.
I don't enable voice chat unless I am going to be using it.
On text chat I do not have chat bubbles enabled. They tend to be annoying anyway.

When you are locking up, if you can still move your mouse, hit CTRL-ENTER and it will switch you from "run in a window" to fullscreen. Sometimes this stops the lockup. Sometimes. Don't quote me on that, though.

Really, it is a hunt for that Red October. It's hit and miss. Find the best configuration for YOU and go with it.