I used unrevoked3 to root. However that is as far as I have gotten. I have superuser permission, but am not sure what to do next. My goal is to be able to install custom roms.
I have a feeling I need to install a custom recovery (I guess like clockworkmod) but I was under the impression that was with unrevoked. What is my next step?
First welcome to Android Central.
You can use clockworkmod but there are known issues. Many have better luck with 2.x.x build. I believe its 2.5 or so.
Me personally, I recommend Amon RA. If you don't feel comfortable yet with flashing manually, then you can add Amon RA or clockworkmod an eaiser way. Get rom manager from the market. From there you can add either one. clockworkmod is at top and amon ra is at the bottom under alternative recovery.
My vote is for amon ra but its up to you.
Once you have one of the two install you need to make a nandroid (backup) of your current stock rom.
Once you do that pick a rom you like and put it on your sd card. (this will be the manually way of doing it). Wipe your data, cache, and dalvik cache. clockworkmod has dalvik under advance, I believe. Once you have that done, choose flash from sd card and then select the rom.
Now the rom you pick will be a personally option. If you like the stock version you can try sprint lovers, if you want a version of stock but without the sense then you can try vaelpak, or there is a 3rd option. Its AOSP (Android Open Source Project), its pure android. Cyanogenmod is a popular one. I'm usnig CM7 nightly builds which is based off of 2.3.3 Gingerbread. there is also CM6.1.2 which is a stable build that is from Froyo.
Important info about AOSP roms. Make sure you get the gapps (google apps) for the rom. With AOSP roms you want to flash the rom first and then the gapps. If you don't get the gapps then you won't have the market and some others as well.
Just read, look around, and flash to see what you like. XDA is good place to check out the roms.
Happy flashing!

It does become addicting lol
If you have any more questions just ask. We are willing to help