Hi, welcome to the forum and to carving!
I love carving cypress knees. The wood is soft and pithy which means you need really, really sharp knives and chisels.
Cedar is good but a very hard wood. Drift wood is a lot of fun and can be good to carve, all depends on what type of wood it is.
Another good option is to buy basswood for carving. I would recommend buying it from Heinekee link attached... I buy all my basswood from them, it is clearly the best wood available.
http://www.heineckewood.com/
Hope this helps a little