We really should create a new FAQ page, but for now, let's collect the wisdom about intents in this forum.
Here's a question on the maximum intent extra size limit and the answer:
http://groups.google.com/group/android-developers/browse_frm/thread/9309...
"The size limit is: keep it as small as possible. Definitely don't put
a bitmap in there unless it is no larger than an icon (32x32 or
whatever).
Regardless of the size limit, having a lot of data in there is going
to have a pretty big performance impact, since it needs to first go to
the activity manager process, which holds on to it the -entire- time
the user can return to the new activity (so that it can be re-created
with the same intent), and then copied in to the process of the new
activity (which may or may not be your own).
Small is good! "