EDIT: Sorry about the less than flatering grammer and what not, class was almost over, as was my procrastonation on the forum hehe.
*Opera Mini Beta 5--Amazing, fastest browser I've used.
*Auto-Lock On/Off--Switch like the integrated Wi-Fi etc. but turns off the Pattern unlock

.
*Car Mode--When activated sends all incoming calls to speaker.
*Touiteur--Great Twitter app, full version has a widget too.
*AudioManager--Show and control system Volume.
*LookOut--Anti-virus-scans every downloaded app, back-up contacts, pictures and call log to their secure online database and recovery if lost, GPS and siren to alert you.
*Where's my droid--Finds your Eris if lost (like in a couch

) plays all sounds at full blast when a secret word is texted to it.
*Unit Converter(Looks like Apple app store icon XD)--Has everything under the rainbow to convert from or to ^^.
*TTS services extended--Text To Speech, useful if you have Handcent (which most do

)
*Robotic guitarist--Can play and see how to play chords. Easy interface. Simple enough for beginners, but has enough to help an experienced guitarist

.
*RingDroid--I'm sure you've seen, heard of or used this before but if not, you can edit any music/media to become your ringtone/notification sound/alarm etc..
*Rhyme Finder--Nice if youre bored, writing (songs, poems etc.).
*My Verizon--See your usage (if you're limited in SMS/Calling) your bill, your last payment etc.
*MobileBuzz--A widget(of sorts) that shows the latest in Android, iPhone or gadget news.
*More Icons Widget--
http://www.droid-eris.com/android-applications/more-icons-widget-*pictures*/ forum post.
*Engadget--Gadget news from three site

.
*Delete Old Messages--Deletes your message threads if you didnt delete them(like I did

hah) it does take a while, but it's the only one i've used that works.
*SMS Quick delete--For those shorter threads(100-250ish) will delete 100+ within seconds.
*Clipper--Allows acces to your clipboard (which seems to be missing on the beloved Eris).
*App List--Creats a .txt file with the info of all of your apps, helpfull if upgrading to the 2.1 leak or just factory reseting the phone.
I think i'm done now haha...
Yep I am ^^