No Tourney or Altus parts on Shimano website?
They still exist - they just aren't high enough in quality/product line to appear on the front page for Shimano (i.e. they aren't useful marketing points for Shimano, but you can still order parts in those groups from most cycling retailers - almost everyone who buys Tourney/Altus is an OEM or a bike shop who needs something very cheap for repairing BSO's; In fact, Tourney does appear on the better BSO's now, and Altus on the bottom rung of non-BSO's which is usually upgraded to Acera/Alivio when needed anyway). 

Here is the link for Tourney and Altus. If those links don't work, go to this link and select them under the mountain bike drop down.

Also, for what its worth, heres something regarding personal experience: My commuter was a 7 speed bike with Acera trigger shifters. They happened to be damaged, and the only new part on the market for 7 speed was Tourney. The only way I could describe Tourney was "starts with s, ends with t, and the word isn't soot" - wouldn't stay in adjustment, horrible brake feel, etc. 

Ended up throwing out the Tourney stuff shortly after, and upgrading to 8 speed and Alivio shifters and brake levers. Its not hard to find the 8 speed Alivio shifters anymore (despite them not being current), and I needed a new freewheel soon anyway (yes, my commuter runs a freewheel, not a cassette), so I took the plunge.