Is there an automatically scrolling, time-delayed Unix pager command?

A simple solution using bash:

function scroll
{
    while read -r ; do echo "$REPLY" ; sleep ${1:-0.5} ; done
}

Usage

long_command | scroll [delay]

delay is optional and defaults to 0.5.

Exit with Ctrl+C

If you can live with 1s resolution, you could do tail -n +0 -f -s <seconds>.

You could use vim with an appropriate mapping to achieve this:

vim -c 'map <S-f20> L:redraw<cr>:sleep 500m<cr><C-d><S-f20>' -c 'execute "normal \<S-f20>"' -

Ctrl-d scrolls half a page at a time, replace with 10j to scroll 10 lines at a time.