One more thing I should add to the "write to the second session on a live CD where you booted from the first session" trick: I found that the DSL linux CD I had made would no longer boot after writing the second session. This isn't really much of a problem, since the real purpose of this exercise was to get recovered files written to a CDR or CDRW and you still have that. The disk can be read as any normal CD. But writing the second session seems to change it enough that it's no longer bootable.

Those trying this might want to use a CDRW, if available, so they can reuse the disc, but if your main purpose is to extract and archive files a CDR should be fine.