well, on the main screen of cydia, there is a spot that says "more package sources". that for one helps a bit, as that will give you more sources to find apps.
Also, it helps to go to other iphone modding sites, such as
www.modmyi.com lots of people and news there about the iphone, apps, and repositories.
Plus, I never know what kind of app/program i'm looking for. So I just tend to test apps that sound interesting. Naturally, some suck ***. But others, are great, and I would hate to use my I-phone without them.
AdBlock is a program I can't go without. blocks ads while online. It costs a couple dollars, but it's totally worth it in my opinion.
I also am in love with MySMS. mainly because it has the ability to let you quick-reply. text messages and your replies will be in a slightly translucent box that's overtop whatever you're doing ( except games. ). If you're online, you can reply to a text without closing the browser. Hell, you can recieve a text, and reply while you are talking on the phone. It's the most handy app I have.
Categories is also another great app. Lets you create folders, and put other apps into them. All my games are in a games app, some of my tools type apps are in a tools folder. Really helps clear the clutter on your spring board.
Also, some of the themes are nice. Right now, I'm using an old style 8-bit gameboy style theme. Everything is green and black, and looks like the springboard is being displayed on an original gameboy screen.