If so, what software have you found to support your study of Spanish? Is there any good free stuff? Any free PalmOS dictionaries worth looking at?

Vocabulary Cards is a good flashcard program for anything you want to learn 

http://www.dolphin-world.de/software/vocabulary.php 

 Any others? 

In the past, threads were initiated by staff, one for each lesson or podcast.
Now we all have ability to create a thread for a discussion, somewhat like we can on a forum.

So, conversation threads can be for either purpose, started by anyone. If you want to say something that doesn't have a suitable current topic, you can create one.

There is also a facility to send a personal message to another user. I tend to avoid using it, because it always tells the recipient what the sender's registered email address is.

I don't use the watchlist feature, and so far haven't felt deprived because of it. If there are particular persons whose conversations you're extra interested in seeing you can add them to your watchlist, and presumably they will be highlighted in some way. Everyone else can see who is listed in your watchlist too, for example your watchlist is displayed beside each conversation (thread) that you initiate. The watchlist feature can also be used to avoid someone you don't want to see. So for example if you find my posts to consist of long boring improperly punctuated whaffle that is of no interest to you, resulting in raised blood pressure and strong temptation to lower yourself to the same standards in response, you could if you wish ignore me.