"Hibernate" seems to be the ultimate core-dump: dump all of memory to the disk, and reload it on power-up. However, I haven't yet used a linux machine where resuming from hibernate was faster than a fresh boot. (Even on Windows, there isn't much difference). The main advantage is that it preserves the state of the system: if I factored in the time to open all the programs I have, reload all documents, webpages, etc, hibernate would be a big win.
Luckily, on my current laptop, "sleep" (suspend-to-ram) works very well, so I rarely do anything else.