Firstly, this thread my fit better in the Tech forum....
I have lots of suggestions for android apps.
http://market.android.comLog in with your gmail account. You can install apps directly to your phone from the website. It's a lot easier than installing from the phone marketplace.
Since you play guitar, start with "gStrings" (awesome Guitar Tuner)
I also use an app called "SoundCloud" which is actually a web service for sharing music/sound files. It allows you to record audio on your phone and upload it to their website to share. MP3 Recorder is also handy for recording, although I don't use it much any more now that I have soundcloud. My phone makes surprisingly good audio recordings.
For SMS, "Handcent SMS" is a great replacement for the default messaging.
"Dolphin HD" is a great browser. Supports tabs, bookmark syncing and saving, and has some nifty add-ons. I understand they had a security issue with their latest release, but I think it's been patched.
Other obvious stuff are the various book/reader apps like Nook, Kindle, Google Books, etc...
If you want to read forums outside of the browser, you'll want "Tapatalk"
I also have a bunch of news apps.
Yahoo News, News & Weather, msnbc.com, foxnews.com, engadget mobile, nbc news, etc... And any apps your local news channels and newspapers might have.
If your bank has an app you might want to put that on there (then again, maybe not).
Any social media apps. I don't use facebook or twitter much, so I don't have those, but I've heard that "Tweetdeck" is pretty good for twitter.
If you keep music on your phone, you might want to check out "PowerAmp". It's a really good music player app, although the new "Google Music" is out now, so it may work fine for you.
If you use Amazon's cloud services, you'll want to download the "AmazonMP3" and "Amazon.com" app to access your music from there.
For a keyboard, I use the default most of the time, but sometimes switch to "Swype". If you can't get it from the market, you can get the app sent to your phone by going to their website and signing up for the beta.
http://www.swype.comThere are lots of fun/free games. We had a 'Paper Toss' tournament at work a few weeks ago. And "Airport Mania" is a fun little time waster.