The Janome Jem line of sewing machines has a really good rep among quilters, and they are lightweight. Here are some websites for them:
http://www.sewingroom.com/jem.htm
http://www.sewvacdirect.com/janome660jem.html
http://www.rosiescalicocupboard.com/
They vary in price depending on features. I think the Jem Gold Plus is the newest one with the most features.