F-Prot, which can be download for free for home users
, is a good option. I liked F-Prot because they offer a file known as the EICAR
Standard Anti-virus Test file. Once you install F-Prot you can use EICAR to test your installation. There's also lots of documentation on the site. I've found it's easiest to set up a Cron job with F-Prot in order to download new updates and scan. Here's a sample of my Crontab for use with F-Prot.
25 8,9,10,11,12,13,14,15,16 * * * /usr/local/f-prot/tools/check-updates.pl -cron > /home/someuser/Documents/update_anti_virus.log
10 10 * * * /usr/local/bin/f-prot -r / > /home/someuser/Documents/anti_virus_scan.log
Hope this helps.