HP printers like the Color Laserjet 2840 include a scan feature, which HP only supports on Windows. However, it's possible to get all the functionality going on Linux, following the instructions in this article by Dag Rende.
You can also access the memory card slot(s) on the front of the printer. Note that memory cards in these slots are pretty much Read-Only; you can't even delete or rename files.
On Ubuntu or Debian, first be sure you have the smbfs package:
sudo apt-get install smbfs
Create a mount point:
sudo mkdir /media/HP
Then, assuming your printer is at 192.168.1.50 --
mount -t smbfs //192.168.1.50/Memory_Card /media/HP
Theoretically you should be able to use Nautilus and just connect to that "Windows" (CIFS / Samba) share, but I wasn't able to get it to pass "no username and no password" ...