Hopefully this will answer some of the more common questions that are being asked. If anyone here has a good root guide or other help info, Let me know and I will add it in...
How to unofficially upgrade Eris from 1.5 to 2.1 Version 3 --
NON ROOThttp://www.droid-eris.com/updates-and-cupcakes/2-1-leak-version-3/How To add Yahoo Email account to Erishttp://www.droid-eris.com/htc-droid-eris-reviews-and-video/all-help-videos-in-one-place/How to do the airplane mode trick if Cell standby is at 50% - Thank you Monty1 for this idea
(It may be possible that it drains the battery when it runs at 50% all the time so this resets it back to normal %) 2.1 version only (if there is an issue on 1.5 please advise and I will edit the post)To check the % :
1) Press Menu / Settings / About Phone / Battery / Battery Use
2) you will then see the cell phone standby %
To reset %
1) Put phone into airplane mode (hold power button till a menu pops up & hit airplane mode)
2) Now press power button again to put phone asleep (You don't have to power off)
3) Wait 1 or 2 minutes and take out of sleep mode and turn airplane mode off
4) Go back and check %, you should see it lower or just wait a few minutes and check again, it will go down.
So far for me, I did it about 3 days ago and it has been staying around 5% since then.
Also it doesn't matter if you plug the phone in or not, it doesn't affect this method.
Mounting the Memory card (For adding files and 2.1 leak)
I will suggest installing a file manager app, it makes managing your memory card alot easier. I use Astro file manager but there are others, just search the market.
There are 2 basic ways1) Put the memory card directly into your PC memory slot (If available) and load the file(s) directly on.
For Version 1.5, if you are trying to mount the phone, go into Menu/settings/Mount Memory card (Im pretty sure thats the location, If not, can someone let me know the correct way)
For Version 2.1
2) Connect phone with usb cable to the phone and pc. A menu should pop up (if it doesn't pop up, just pull the notification bar down and press charge only to see the other options) asking if you want to:
Charge Only
HTC Sync
Disk Drive

3) Pick disk drive & press done. Your phone should show up under my computer as a removable drive & a popup window will ask if you want to view the files on the card.
4) Open & view your memory card files. Drag & Drop / copy & paste the file to the card.
5) If your putting the 2.1 leak on the card, DO NOT change the name, UNZIP or alter the file in any way. Also drop it onto the card DO NOT put it into any folder...
6) When done, pull down the notification bar & pick charge only & wait for a few seconds, then disconnect.
Root Info & LinksThis is just some links to root PLEASE USE CAUTION & READ CAREFULLYhttp://www.droid-eris.com/updates-and-cupcakes/the-eris-has-been-rooted!/http://forum.xda-developers.com/forumdisplay.php?f=554