Inkscape may still crash, it's not perfect (although we try hard).
If it does so, then it will try to save the document you were working on.
[edit] On Unix (Linux, Mac OS X, *BSD, ...)
Inkscape will try to save to
- your home directory as
filename.<datetime>.# -
/tmp/filename.<datetime>.# - the current directory as
filename.<datetime>.#
(in that order).
If the document does not already have a name, the filename is inkscape-emergency<datetime>.#.
Note that the saved file will not have the .svg extension!
[edit] On Windows
Inkscape will try to save to:
C:\Documents and Settings\<yourname>\