If you have a working internet connection best place is the repository. A well set up repository can let you access lots of softwares.
Here's mine /etc/apt/sources.list
Code:
deb http://archive.ubuntu.com/ubuntu dapper main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu dapper-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu dapper-security main restricted universe multiverse
deb-src http://security.ubuntu.com/ubuntu dapper-security main restricted universe multiverse
deb http://packages.freecontrib.org/ubuntu/plf dapper free non-free
deb-src http://packages.freecontrib.org/ubuntu/plf dapper free non-free
deb http://archive.canonical.com/ubuntu dapper-commercial main
deb http://wine.sourceforge.net/apt/ binary/
deb http://wine.budgetdedicated.com/apt dapper main
deb http://deb.opera.com/opera/ etch non-free
deb http://kubuntu.org/packages/kde-latest dapper main
deb-src http://kubuntu.org/packages/kde-latest dapper main
deb http://kubuntu.org/packages/koffice-latest dapper main
deb http://kubuntu.org/packages/amarok-latest dapper main
deb http://compiztools.free.fr/debian unstable main
deb http://www.beerorkid.com/compiz/ dapper main
deb ftp://cipherfunk.org/pub/packages/ubuntu/ dapper main
deb-src ftp://cipherfunk.org/pub/packages/ubuntu dapper main
deb http://nightlies.videolan.org/build/dapper-i386 /
deb http://download.skype.com/linux/repos/debian/ stable non-free
So, you can manually download deb files from these sites manually too. But, then it will be difficult to manage the dependancies.
Also, some packages in my repositories are betas, I would advise you not to install them for now.