Grant, check back at about half 2 and i'll post up some of the best sources for themes, apps and tweaks. At work at the minute
**EDITED**
First thing you'll want on a Jailbroken iPhoen is Installous. Check the first page how to get this.
Right, Cydia will only show files from sources that you have added into Cydia itself. To do this follow this:
1) open cydia
2) press manage (bottom right)
3) press sources in the middle
3) press Edit (top right)
5) press Add (top left)
6) type: (Link here) and press add source
7) press Add Anyway
Following links are great sources!
xSellize:
http://cydia.xsellize.com - This is for tweaks such as infinite apps in folder, infinite apps on dock. Way too much to list. Also superb for free THEMES!
SiNfuL iPhone:
http://www.sinfuliphonerepo.com - Same as above
Hackulo.us:
http://cydia.hackulo.us - Mainly for Installus but there is other stuff too.
TIP: If you go into "Cydia>Sections>Repositaries>" You'll find links you can download straight to your iPhone. One is called "All repositories" or something.
Anything else, feel free to ask!