With the default US keymap, you can use Shift with the PgUp and PgDn keys. (The gray ones, not the ones on the numeric keypad.) With other keymaps, look in /usr/lib/keytables. You can remap the ScrollUp and ScrollDown keys to be whatever you like.
The screen program, http://vector.co.jp/vpack/browse/person/an010455.html provides a searchable scrollback buffer and the ability to take "snapshots" of text-mode screens.
Recent kernels that have the VGA Console driver can use dramatically more memory for scrollback, provided that the video card can actually handle 64 kb of video memory. Add the line:
to the start of the file drivers/video/vgacon.c. This feature may become a standard setting in future kernels. If the video frame buffer is also enabled in the kernel, this setting may not affect buffering.
In older kernels, the amount of scrollback is fixed, because it is implemented using the video memory to store the scrollback text. You may be able to get more scrollback in each virtual console by reducing the total number of VC's. See linux/tty.h.