I wrote this paper for the Sfonge.com knowledge exchange. This tries to put all sorts of "widget" technologies into context, including Android widgets (you need free registration to get this page).
I could not figure out, how to place a direct link, just look for widget.pdf on the page. Update: direct link to the document.
Back to the main issue: I found a nice confusion with regards to the widget term itself. Basically there are two schools: one interprets widget from the user's point of view, as a mini-app on a default screen, e.g. home screen, the other approaches from the technology point of view and considers widgets as locally installed web applications. There are interesting corner cases. For example Android widgets are full-featured widgets from the user's point of view but not widgets from the technology point of view because Android widgets are not based on web technologies. Blackberry widgets, on the other hand, are based on quite sophisticated web technology engine but they are always full-screen. This is not that an ordinary user would call widget.
Anyway, I am looking forward to your comments either here or on the Sfonge.com website. I will also get the direct link to the document, don't worry.
On a personal note, I am back to Budapest from London. The 2-year UK vacation is over. Gee, I started this blog before I moved to London and now I am back. How time flies - particularly in the Android universe.