you can usualy make a textfile by using the > sign. like this
Code:
dpkg -l>packagelist.txt
this is just the dpkg -l with output redirected to create a new file called packagelist.txt.

As to getting several pages of text, using the | sign (that pipes output to the next program) and another programe called a pager, pagers are programs that shows output one page at a time, comon pagers are; more, less and most. so typing
Code:
dpkg -l|less
and using page up/page down keys will alow you to look trough that mass of text.
if you want to use a "searchword" like KDE or GNOME. you can use a comand called grep.
like this,
Code:
dpkg -l|grep kde
now just things containing kde will show up in output.
you can even combine them, for example like like this
Code:
dpkg -l|grep kde|less
have fun
OErjan
EDIT if you want to learn basics of the comandline http://floppix.com/index.html has a great lab page that will teach you the basics fairly quickly.
here is the direct link.
http://floppix.com/labs.html
/EDIT
PS
if you have a console open in X (graphic environment) you can copy/paste with the mousewel or both right/left button simultaniously. works in textmode aswell but... limited.
DS