The following is a list of commercially available shoujo anime for Region 1 (North America). All DVDs feature Japanese language with optional English subtitles and (usually) an English language track. The list of out of print titles is current as of January 2008 (Ceres may also be/be going out of print - the Collector's Edition Box Set 2 appears to be OOP). Titles released after March 2007 are not yet listed.
As anime series are frequently reissued in various formats (singles, box sets, thinpaks, etc.), I have ceased linking directly to the DVDs on RightStuf in most cases. Links are provided for titles which are either one volume or have their own category on RightStuf. The others can be accessed using the RightStuf search. It's a good idea to check the AnimeOnDVD disc reviews to see how many volumes are in a series and how they are being released. Wikipedia can also be a good source of information on DVD releases of individual series.
Studio Ghibli produces many excellent films for general audiences that are well suited for young female viewers (this is remarkable only because it is nearly unheard of in North America for general audience films either animated or live action to feature a girl as the protagonist - thank you, sexism).
Yaoi Suki provides very helpful reviews of Boys' Love titles.