Going in machines and processing lines? You all have talked about maceratrons and variants (pulverizer and co), furnaces (or maybe not), and even the electrolyser, but there are much better places to go. What about all this gregtech and TE stuff? And why only players would move in pipes? Let's put some mobs in them and send it around our processing lines.
Sawmill? meh.
Extractor? maybe. I don't really know what is going on in it. Looking in would be a good idea. By the way, putting mobs/players in should make some MFR mob essence.
Canning machine? Filling my shelves with creeper filled cans sould like a good idea. I'll sell them as food on the server.
Recycler? Would be a nice way to dispose of silverfish.
The blast furnace (i'm talking about the chrome one wich smelt tungstensteel) look much more fun than a regular electric furnace, and the vacuum freeser look not bad too.
Magma crucibles? Would be more interesting than macerators for unwanted players.
Fusionreactor material injectors? Even better.
Compressors? meh. But the compressor is just a open door to another much better machine: The implosion compressor. If i have to end in some machine after falling in my pipe system, i want to go here. It's just awesome. I mean, a box where you put stuff in and blow it up with 10 TNT at the same time.
If you're lucky enough to go to the storage room (or you just exited a prossesing line, alive or not), you will first collide with all the stuff coming from some quarries and the prossesing lines, then go into a sorting system, wich will probably put you in the misc chest, because i don't know any sorting system with a player output. Or you can end in another chest. Some chests/barrels/DSUs/other are for cobblestone and other stuff wich comes in large quantities, and ending in them would be not the best choice, as you will be quickly buried under the flow of incoming items. And those large amount storages can have a overflow system (because a bunch of bilions of cobblestone is enough) so the overflow ends into a incinerator/void pipe/recyclers.
You still want to go in tubes? You'll want another tube network, however, you'll see what being a ore look like. Have a nice day in the processing line.