httpd(apache), dunno if it comes on the ubuntu cd's. Just install and it should be ok with the default config. Dump files for remote (and oh so public) access on the webroot dir (/var/www ?). You may even setup some small html or any of the free software tools to help with the browsing and optional authentication.
ftpd (prolly best bet). Any of the ftp servers that come with linux should be fine. May require some RTFM to kickstart the server. Then you just ftp with your ftp client or even web browser to access files.
samba (hardest to setup, easiest to use). After the ceremonial RTFM you can mount your files as a netdrive from any (even windows) machine.
for the new hdd:
mk2fs (or was it mkext2fs?), after partitioning ofc with cfdisk.
Then to automount make appropriate entry in /etc/fstab (or from some of the ubuntu tools that I have no idea what they are).
I bet though that ubuntu comes with a tool that does all that, check the system tools.
