AVG has a free version for Linux that is easy to use and has a GUI
interface.

ClamAV is in the Ubuntu repo's and has an GUI (clamtk). ClamAV is a
little more difficult to setup as you will have to edit text files and
read the manual.

That would be avscan. Most of the antivirus stuff can be found in synaptic. Your
chances of getting a linux virus is so low. It is like being stroke by lighting.
Most of the virus scanners are for email apps. Like if you get a exe attachment
in your email and want to scan it before forwarding to a windows user. Windows
virus will not affect at all a linux/unix O/S. If a virus does happen. It cannot
at all attack the linux kernel. Like a virus for winodws. It attacks the hole
windows kernel. It can only get a program or so. And all you need to do is
reinstall a effect program. I been running linux for 5 years now and yet to see
a linux virus and be effected by one. I never seen any one get a virus at all.
All linux/unix virus have been created in a lab and self contained. All so you
need to be log in as root user to invoke a virus for linux/unix.
To use av scan just load up in synaptic. And a good rule a thumb is look in
synaptic first before going through all the trouble of DL from the net of RPM.
TAR, or DEB. To run avscan after the install is open up the terminal and type in
avscan.

this is becoming exciting like learning a new thing such as
this. i didn't have much idea that there are a lot other packages in
synaptic (i found the openoffice.org the other night) until last night
when i was looking for the firestarter. went to the ubuntu site and
did some reading on how to find the firestarter. it directed me to the
synaptic.

installed the firestarter and lots of other software package i
found.in summary, virus infection should not really much of a concern
with linux. this is great.

Well, its true that you don't get Linux virus (99.99999%) . In my case
I was extra cautious. I installed clam AV on my Kubuntu. With a smile
I ordered it to scan. To my horror it found 64 problems (Not viruses
!). When I Quarantined it, I found my NetBeans IDE (used to develp
Java and C++) programs was virtually destroyed.

Clam AV, if it finds a large ZIP, JAR or GZ file, quarantines it, even
though it may not be virus! So if you are using SUN Java development
tools CAREFUL!!

Well I think it advisable to go for a tried and trusted virus protector,
Although Clam makes lot of self claims its very new on the scene.