I got an permanent resident vise in may and moved to the USA, when I came in the immigration clerk stamped my passport with a stamp that says its valid for one year from today. I'm expecting to go on vacation to europe in June and would like to know what I need to do to be let back in to the US? Do I flash my Green-card? Do I need to get a new vise in my passport?

Welcome to the US. You should be receiving your permanent resident card (I-551) in the mail at your US address of record shortly. You should travel using your I-551 and your current passport. If you don't receive your card timely, go online to the USCIS website and schedule an INFOpass appointment at the local district office for them to stamp your passport with evidence of your US permanent residence.

It isn't clear from your post as to when you entered the US. The card usually comes in the mail about 3-6 weeks after entry. Hope this helps.

If you don't receive your card within that timeframe, you should file an I-90 for a replacement green card.