What are the most popular iPhone third party apps?

I know that “ipipes” is one of them

There are a lot of “unofficial” third-party apps available. They require “Jaibreaking” your iphone, however, which you may or may not be willing to do. Although my phone is Jailbroken and unlocked, I haven’t really found any overly compelling 3rd party apps. Most of them I uninstall after a couple days. Flashlight, is probably the most useful (it just sets the screen all white at max brightness for a very effective flashlight with your phone). iTwitxr is kinda neat (takes a photo and sends it to twitter) and iAno is too (piano simulator). I also have iFob installed, which lets you meet other iPhones nearby – but nobody else seems to use it. Other than those, though, I only have a few utilities installed (VNSea, Term, etc)

There is an interesting Skype webapp (jailbreak not required) that basically lets you call your Skype account and it will connect you, via Skype, to another party… useful for saving long distance charges… you can find it listed here:
http://launchrz.com/links/show/220

Here’s a list of usefull iPod Touch apps that might be ok for the iPhone

what is ipipes?