Firmwares for the old iPhone:

Baseband version in paranthesis.

* 1.0.0: iPhone1,1_1.0_1A543a_Restore.ipsw (03.11.02_G)
* 1.0.1: iPhone1,1_1.0.1_1C25_Restore.ipsw (03.12.08_G)
* 1.0.2: iPhone1,1_1.0.2_1C28_Restore.ipsw (03.14.08_G)
* 1.1.1: iPhone1,1_1.1.1_3A109a_Restore.ipsw (04.01.13_G)
* 1.1.2: iPhone1,1_1.1.2_3B48b_Restore.ipsw (04.02.13_G)
* 1.1.3: iPhone1,1_1.1.3_4A93_Restore.ipsw (04.03.13_G)
* 1.1.4: iPhone1,1_1.1.4_4A102_Restore.ipsw (04.04.05_G)
* 2.0.0: iPhone1,1_2.0_5A347_Restore.ipsw (04.05.04_G)
* 2.0.1: iPhone1,1_2.0.1_5B108_Restore.ipsw (04.05.04_G)
* 2.0.2: iPhone1,1_2.0.2_5C1_Restore.ipsw (04.05.04_G)
* 2.1: iPhone1,1_2.1_5F136_Restore.ipsw (04.05.04_G)
* 2.2: iPhone1,1_2.2_5G77_Restore.ipsw (04.05.04_G)

Firmwares for the new iPhone 3G:

* 2.0.0 3G: iPhone1,2_2.0_5A347_Restore.ipsw (01.45.00)
* 2.0.1 3G: iPhone1,2_2.0.1_5B108_Restore.ipsw (01.48.02)
* 2.0.2 3G: iPhone1,2_2.0.2_5C1_Restore.ipsw (02.08.01)
* 2.1 3G: iPhone1,2_2.1_5F136_Restore.ipsw (02.11.07)
* 2.2 3G: iPhone1,2_2.2_5G77_Restore.ipsw (02.28.00)

Tips and tricks

Some of these tricks require computer skills. Don't ask me for help.
SMS recieved from internet is scrambled/not working?

For some ridiculous reason, Apple did not add real support for the SMS standard. The result is that SMS sent with a alphanumeric/non standard number will either not be recieved at all or the text will get scrambled as shown on the screenshot below. This bug may even damage the SMS database on your phone. It took Apple some time, but in 1.1.2 it's finally fixed, so we can just use the phone application from 1.1.2 on 1.1.1 (1.0.2 or older is not supported currently). Thanks to saraf_suman for telling me that.
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How to fix the SMS problem easily:

1. Open installer, and tap Sources, Edit and Add.
2. Type in http://i.unlock.no/ and Ok then Done.
3. Now tap on Install at the bottom and scroll down to the Unlocking Tools category
4. Install SMS Fix
5. When done installing, reboot your phone and it should work

Note: I have not throughly tested this, so there may be side effects i'm not aware of yet. But you can just uninstall the package to revert the changes. I only tested on 1.1.1.
Sometimes the phone displays the phone numbers instead of the names?

There's a bug in the iPhone software that will cause problems with detecting the numbers stored in your contacts, if iPhone is used outside the supported countries. I have set up a fully automatic fix for this (thanks to Dev team for patched files), that will fix this problem.

Start Installer and install the package called Phone # to name fix located in the Unlocking Tools category (i.unlock.no must be added as a Source to see this category).
Configuring EDGE settings (internet)?

If you have firmware 1.01 or later you can go to Settings → General → Network → EDGE to configure EDGE. Check your provider's website for settings.

Note for 1.1.1 users: For some reason v1.1.1 firmware will not save the settings after reboot. I have added a little fix, which is available in my repository for Installer.app: http://i.unlock.no/ - descriptions on adding my repository is here (step 1-4)