Yep, the easiest way is to simply extract your war into the server/default/deploy/ dir. If you made changes simply touch the deployment descriptor and JBoss willr edeploy.
Just remember the directory you put the unpacked war into has to be named xxx.war where xxx is the context you want to use. And you don't have to "touch" the descriptor file if you're changing JSPs ... you can either copy a new one over the top of the old one, or even edit it "in place" (caveat emptor). The next time the JSP is accessed, the new timestamp is noted and it's recompiled.