If you haven’t yet entered our Share the iPad Guide Giveaway, this weekend is your last chance to do so. To celebrate the release of The iPad Buyers’ Guide + Free iPod/iPhone Book 5, iLounge is offering our readers a chance to win some great prizes for sharing the Book with friends, family, and social network followers. To enter, simply retweet this message—complete with bit.ly link—to your followers. 50 retweeters will be selected…