Module development and code questions

I have recently installed Drupal and have been quite pleased with its capabilities. I'm interested in creating a site that would require users to submit content over several pages. I would be asking for a fairly large amount of information from my users which is the reason for the multi page submit process.

Two questions:

Just a simple and stupid game to keep your users busy. :)

It's just like the 'game of tag'.

You can check it out here:
/cvs/contributions/module/taggame

Have fun.

I would like to develop a module or patch that would allow users to hotlink their images from
another site rather than uploading them, given the problems I've had with uploading currently.
(images go up, they appear in the files areas, they have full permissions, but only the default
avatar ever appears. Vers 4.4.2)

I'm using the book.module now to acheive multipage documents (as far as I could discern, this is the only way...), but there are some unclarities that I have met:

1. Book Metaphor

Intuitively, the book would seem to be a 'binding' and a series of sub-elements (pages, chapters, etc.) The current structure seems however to create a hierarchical tree. In this way, Chapter (or page) 2 is the child of Chapter 1, and it is this relationship that binds them together. This is unlike a book, in the sense that a book's Chapter 2 is sequentially subsequent to Chapter 1, but not necessarily hierarchically so. In order to be more like a book, the module would create a 'binding' or 'cover' which is a parent, and the chapters would be hierarchically equal, but sequentially determined. In this model, the book module would provide two settings: 'parent' and 'sequence'. While parenting could be multiple (Chapter 3 is the parent of Part 1 which is a parent of Book), sequence would be single and individual. This is now not possible now AFAIK...

2. Menu presentation

The upshot of a 'binding' would be that a collapsed menu could be presented that shows the binding, and when clicked expands to show the child nodes. This would be very useful.

3. Categories

I seem to remember that in earlier versions of Drupal (i'm in current cvs) books pages could be assigned taxonomical terms. I don't have an old install to check this on. At the moment, I can find no way to assign terms to pages or books. Am I missing something?

Something else which may be of use to somebody:
A module which displays the number of nodes which have changed over a certain period on a lineplot.
I use this to have a quick overview of the 'busy' site periods.

This module, like seqgraph, depends on the jpgraph libraries.

You can check it out of the cvs tree here:
/cvs/drupal-contrib/contributions/sandbox/geek/activity/

I'm trying to add a feature to my filter to not run on comments when so configured. However, none of the filter hooks seem to pass on what kind of node the text is originating from. What's the best way to execute this? Is it even possible to detect at the filter level?