I have started making some small Java games that run in a browser and have found a couple of game portals where I can host then (GameJolt.com, JavaGameTomb.com and Games4j.com). Most of the other portals I find either only allow Flash or offer the games for download.
Apart from those above, what other portals exist that allow hosting applets?
In my experience, it seems that Sun is not supporting Applets as much as it used to, instead preferring Java Web Start. My experience with applets has not been ideal, and others have had problems with it as well, especially in newer versions of Windows. I think that is probably a large part of the reason you are having problems finding applet hosting sites. However, for rich clients, I think Java is an excellent development system.
Just my 2 cents.