I moved your post over to Adventure Game Discussions, as from time to time our GameBoomers member, Chief, provides updates in this forum when new games are added to the list.
There are many good games on the list. I have played some of the free adventure games and found them to be quite entertaining, and you don't have to worry about the downloads containing viruses or malware - but you can always run a virus scan on them prior to downloading if it makes you feel better to do so.
Some of our forum members here might be able to offer some recommendations, as well.