There are lots of great online classes available now for older kids (and parents too).   My favorite is ITunes U.  I download the lessons and listen in the car.   – You can even set it up to listen on your computer through Itunes or on any MP3 player. 

Some others that were listed in Family Circle recently include:

Einztein.com – A mix of schools, museums, and more.  It even includes some social networking features to let you meet and share with other students.

AcademicEarth.org – An indexed set of linked courses available around the world.

LiveMocha.com – A resource for learning a language. Currently there are 35+ languages available.

These great resources aren’t just for kids.  Even college students and parents can use these sites to study up on subjects of interest.