Debian on old or slow computern

Consider using OldStable or Stable. Add Backports to your repos to get more software.

Replace websites with special software

Use youtube-dl -f fmt (e.g. 36) to download videos from Youtube and play it with mplayer or vlc. The english Wikipedia article has a list of supported formats.

If your computer is too slow for iceweasel showing OpenStreetMap, try foxtrotgps.

xbmc or xbmc-standalone (xbmc with X but without a window manager) with radio, youtube or Mediathek plugin may or may not be useful for old computers (xbmc requires 24bit colors).