Hi Debbie,
Currently, Ariel is only appearing for pictures in her human form. She along with other characters from the Little Mermaid appear intermittently throughout the day at the Adventureland Veranda Gazebo at the Magic Kingdom (MK).
You can also see Ariel in the
Celebrate A Dream Come True Parade held most afternoons in the Magic Kingdom.
Ariel does appear as a mermaid in the
Voyage of the Little Mermaid at Disney's Hollywood Studios but there isn't a photo opportunity with Guests during this experience.
Ariel has also been known to appear in her human form at
Cinderella's Royal Table at the MK & the
Akershus Royal Banquet Hall in the Norway Pavilion in Epcot. There are no guarantees which princesses will appear - it varies - but both of these locations are excellent dining locations.
Be sure to check the
Times Guide when you enter the parks for character appearance and performance times.
Times Guides are available at the entrance of the parks, Guest Relations and most merchandise locations.
Under the Sea: Journey of The Little Mermaid is a new attraction that will open as part of the Fantasyland Expansion (no opening date yet although most attractions should be open by 2013). I haven't heard anything concerning a meet & greet in this area yet but it would be great to meet Ariel again in her mermaid form.
Wishing you many magical memories :-) Allison