Hi.

Can I download a program or do something that lets me join set channels when I log onto a server?

Thanks.

You can find many autojoiners in one of these sites
www.mirc.net
www.mircscripts.org
www.mircscripts.com
www.scriptheaven.net

Ofcourse you can use the inbuild autojoiner of mirc (Click the 3rd icon from the left in toolbar =the one with the name Favorites ) and customize the channels you will join in each net from there,but in build autojoiner doesn't have a delay so if you are an opper in one of them for example you will join all channels before you identify your nick.
So you need to Op manually after you join

great.

thanks very much.