FOSS packages that are part of the browser engine:
tablet-browser-daemon
browser-eal
libgtkmozembed
microb-eal
microb-engine
libnss3
libnspr4
microb-engine-common
browser-neteal
libnss3-certs

Closed source packages that are part of the browser UI:
tablet-browser-ui
osso-browser
tablet-browser-view
tablet-browser-controls
tablet-bookmark-manager
tablet-browser-dialogs
tablet-browser-widgets

Other things that talk to microb: (on a stock Fremantle system, no clue about Extras)
rtcom-messaging-ui (closed source, uses tablet-browser-view and browser-neteal to talk to browserd)
tablet-browser-view-test (open source, uses tablet-browser-view and browser-neteal to talk to browserd)
nokia-maps-core (closed source, talks to microb via browser-eal)
modest (open source, seems to want microb-engine but also gtkhtml, not sure what its really doing)
libmaemosec-certman0 (open source, wants libnss3 for some reason)
tutorial-home-applet (closed source, uses browser-neteal to talk to browserd)

Plugins that work alongside microb: (on a stock Fremantle system, no clue about Extras)
adobe-flashplayer (closed source, implemented as an NPAPI plugin)
libssoautologin (closed source, implemented as an extention with a .xpt file, a .jar file, some .js files and a .so file)
microb-geolocation (open source, implemented as an extention with a .jar file, some .js files and a .so file)
nokia-maps-core (closed source, implemented with 2 NPAPI plugins plus some browser components as .so, .xpt and .js files)
tablet-browser-default-plugin (closed source, implemented as an NPAPI plugin)
tablet-browser-mediaplayer-plugin (closed source, implemented as an NPAPI plugin)