Tiffany has a nice simple set...here is the link.

I always go for glassware by Iitalla, which is modern and classic at the same time. There are a couple of different lines on Unicahome.com but my favorites are these:

http://www.unicahome.com/p8072/iittala-hackman-rorstrand/essence-glassware-by-alfredo-hberli.html

http://www.unicahome.com/p13649/iittala-hackman-rorstrand/senta-glassware-by-alfredo-haeberli-for-iittala.html

There's a place in Wilmette called the Crystal Cave (bad name, good quality items) that carries a large selecton of crystal stemware and specializes in engraving.
http://www.crystalcaveofchicago.com/

Waterford crystal is always a classic!

For something still classic, but a little bit different, I totally love the Marc Jacobs for Waterford champagne saucer glasses. They seem so 1920's!
http://www.waterford.com/shop/product.asp?sku=13143&cat=All&terms=169

yay, thanks for helping me figure this out!

You might want to check out lushLYFE.com. Their "Pure" champagne glasses are great. The crystal is made with titanium and they are incredibly strong. Plus, since they're sold in a set of six, you're really giving a gift that is more functional in the long run... most celebrations in their future will require more than two glasses...

http://www.lushlyfe.com/product_info.php?cPath=63_80&products_id=27&osCsid=80e91c6b4cfe0caeb9daa61af6eacca5

Hi, for classic, iconic Scandinavian design have a look around on eBay for Holmegaard (Denmark) Princess range glasses designed by Bengt Severin circa 1957. They're pure modernist styling with an enclosed teardrop to the angular bases - your sister will be forever thankful and, trust me, everything tastes better from them!

amendment: the designer's name is Bent Severin.