Outside of the stuff I've mentioned in this thread, the only other thing I do is jailbreak it. Jailbreaking is super easy to do, but there are a couple drawbacks and I wouldn't recommend it to a casual user. First, you have to wait for official Apple updates if you want to keep your jailbreak. I haven't upgrade to 5.1 yet because there isn't a jailbreak for it... that's not such a big deal since 5.1 didn't bring anything great to the table, but it could be an issue with another update. Second, the hacks here are stuff that go into the operating system and it's important to keep them updated through Cydia (the jailbreak store) otherwise you might have issues. If you are a person who doesn't check for upgrades often, jailbreaking probably isn't for you.
That said here are a bunch of great apps (some paid, some free) that I use that are jailbreak only:
Tru Print: Print wirelessly with any wireless printer, not just airprint enabled printers. This is the #1 reason I use jailbreak.
Retina Pad: Full screen and sharpened iPhone apps on the iPad. All apps now look great no matter if they're iPhone only or not.
Folder Enhancer: Folders within folders.
Manual correct: Gives you the option to use auto correct the opposite way, if you want it to correct you tap on the word. Also, allows you to do this and still autocorrect punctuation and capitalization.
I can't remember the name of the tweak, but I have one that merges the address bar and search to give an experience more like Chrome. This is one of my favorites.
User Agent Faker: I don't use this too often because usually websites are mobile for a reason but some sites work better on the iPad in their desktop version. User Agent Faker allows you to trick the website into thinking you are browsing from your choice of a handful of browsers.
3G unrestrictor: This is one I like on my phone since I still have an unlimited plan, but if you purchase 3g and have a big plan, it allows you to download anything from the app store no matter what size it is and podcasts as well. Oh, and it allows Facetime over 3g which could be a big deal for someone.