Unless these links have a nofollow tag, they send some of your sites PR to the other sites. So the basic answer to your question is "yes". However, there are easy ways to minimize the amount of PR that your site loses. Also, many SEO experts believe that outlinks to high quality relevant "authoritative" sites can actually improve your rankings indirectly by increasing the "trustrank" of your site. So some outlinking, if done carefully and prudently, can be beneficial, despite the loss of PR.
it depends if you are linking to a authority site in your niche, google likes to see outbound links too, how do you think a spider works
i was thinking its kind of a teacher student relationship. by spreading knowledge, teacher's own knowledge do not go any lower but student's knowledge go higher
It's hard to be totally sure when it comes to PR issues. Commonly outbound links (that don't have a no follow tag) take some power from your site and give it to ones they go to. The less OBL's site/page has the more power it gives to sites it links to. Though it doesn't mean that no matter how many OBL's you have you give away the same power. The less OBL's you have the less power you share. Interesting?..
yes, but you dont give presents at christmas just to get one back. google knows if you are linking to a ontopic site and if that site is of more relavence than yours then you will gain from the link because you are providing more resource to the end user. as for nofollow and dofollow tags i cant comment on that yet as i have not tested or done much reading on it yet.