i've heard that google penalizes your site if you have outbound links pointing to an unreliable/spammy/low PR website. if so, then is the opposite true in regards to having outbound links pointing to authority sites?
Some people say it helps but most say your giving away Pr so it does not help. I do not think it helps Pr but it does help anyone who goes to your site find more info on your topic so it makes site better.
google will punish you, if you give link to a spam site or a link farm but it will not punish you when you give a link to a low pr site
Punish might be a bit harsh of a term but I do think you can expect to have a some level of impact when linking to known link spam sites. Remember just because a site has a low PR does not mean it isn't a quality site. Everyone needs to start from somewhere. In fact if you are dilligent you will greatly benefit from linking to quality low PR sites as they will only gain momentum as time goes on.
outbound will not help your site though partly with reciprocal link exchange that is needed...so why have OBL to unnecessary sites...
Just be honest with your links. There's no reason in linking to a spam site. Linking to high authority sites will not help any unless they are linking back.