Jailbreaking your iPhone has been kept legal through 2015 under an exemption in the Digital Millennium Copyright Act (DMCA). The crazy catch is that jailbreaking the iPad has technically been made illegal, while the iPhone and iPod touch both remain exempt.
There are 2 major players in the Mobile phone market. Apple and Android devices and to a small degree Blackberry and Windows. Find sources to your favorite apps to download for free. The majortiy of apps are available through iTunes and the Google Play store but occasionaly developers release them through independant channels. If you have a jailbroken phone or rooted android device then the below sources can give you access to addtional apps for free.
You will first need to jailbreak your phone. Jailbreaking does not damage the phone if performed correctly.
SiNful iPhone - http://sinfuliphonerepo.com
xSellize - http://cydia.xsellize.com
Insanlyi - http://repo.insanelyi.com
PwnCenter - http://apt.pwncenter.com
iHacks - http://ihacksrepo.com
iCauseFX - http://repo.icausefx.com
HackYouriPhone - http://repo.hackyouriphone.org
P0dulo - http://p0dulo.com
BiteYourApple - http://repo.biteyourapple.net
Appcake - http://cydia.iphonecake.com
AppAddict - http://cydia.appaddict.org
Bigboss - http://apt.bigboss.us.com/repofiles/cydia/
iF0rce - http://apt.if0rce.com
ModMyi - http://modmyi.com/repo/
Ryan Petrich's repo - http://rpetri.ch/repo/
FilippoBiga's Beta Repo - http://filippobiga.me/repo
ZodTTD's Beta Repo - http://cydiabetas.zodttd.com/
Pushfix - http://cydia.pushfix.info/
Hashbang - http://cydia.hbang.ws/
You will need to have a file manager app installed on your mobile to have the ability to copy files into a specific location. Using a computer to transfer the apps makes it much easier to manage.
F-Droid - https://f-droid.org/
Getjar - http://www.getjar.com/
AppBrain - http://www.appbrain.com/
SlideME - http://slideme.org/
MobiHand OnlyAndroid - http://onlyandroid.mobihand.com/
Appsfire - http://appsfire.com/
Aproov - http://www.aproov.com/
AppRob - http://appxg.com/