"'Lillie' noted that in practice, the long-and-lacy often turns into the short-and-sassy: 'Melissa gets called Mel, Jessica becomes Jess, Samantha is Sam and Alexandra is Alex. Often these stick enough to become the person's day-to-day name.' 'Melissa' agreed with that point, but added 'I also see a bit of a trend towards using the full versions of names.'
Nicknames can definitely turn a name's style inside out -- there's a world of difference between Gertrude and Trudy. And sure enough, many parents today are rejecting traditional nicknames. (See 'The new formality.') But some parents are taking advantage of the style contrast to let them have it both ways. Alexandra/Alex is sumptuous and boyish. You get two names in one, which part of the name's soaring appeal."
Robert Johanson, East Rift Valley Potentate, and Grand Poobah of Hualien, recommends this site, The Baby Name Wizard. Names gaining rapidly in popularity, apparently, include Aidan, Caleb, Griffin, Mackenzie and Nadia. Names that have seen better days: Betty, Deborah, Pearl and Bill. The creator, Laura Wattenberg, has graphed hundreds of names, charting their relative fortunes over the decades. There's also a cool blog, quoted above.