Here are some I've collected with the help of my fellow forum members. They are listed in no particular order.
http://s83.photobucket.com/albums/j319/pcarrell/Track%20Plans/
http://www.trainplayer.com/Site2/Track%20Plans.html
http://www.cke1st.com/m_train2.htm
http://carendt.us/index.html
http://www.layoutdesigns.com/
http://www.vetmed.auburn.edu/~smithbf/BFSpages/LDSIGprimer/TOC.html
http://home.earthlink.net/~mrsvc/id9.html
http://home.earthlink.net/~mrsvc/gallery/index.html
http://home.earthlink.net/~mrsvc/id28.html
http://home.wanadoo.nl/reinoud.kaasschieter/railway/index.en.htm
Not all of them are total trackplans, but they can be a good source of ideas.
FT