Advice needed on which distribution, method of download.

I recently installed Mandrake 8.1 from from an .ISO file from disk one.
Something seemed to go just a bit wrong during the install when some
packages were listed as uninstalled.
Inspite of the warning, it installed for my matrox g450 and works better
than any linux I've used to date.
However, I'm installing linux for 2 reasons. First, I just want to expand my
experience with Linux, and second, I want to create an environment for
learning Java, Python, C, Tcl, shells, etc. I need to get sharp as a
programmer.
Which dist would you recommend?

As far as method, I have broadband so downloading is fine.
I have some cds from LinuxMall. I believe I can install with these and then
use upgrade features or simply download files and install from them. I
don't know which to do as some methods have hidden problems to the
unexperienced.

These are the CDs I have:
Linux-Mandrake 7.0
Official Debian GNU/Linux 2.1 Disks 1 & 2
Red Hat Linux 6.2
Caldera OpenLinux 2.4
SuSE Linux 6.4
and FreeBSD 4.0 to finish the collection.

I tried to install the Debian just for the challenge. I don't remember what
went wront but it didn't install. I tried Mandrake 7.0 but one of those two
just left a black screen.

First I need to decide upon a distribution, then a method of installation.

Suggestions welcome.