. First of all, I am going to be explaining what item is gained in that secret area rather that explaining how to get to each one (of course i will do this in the actual guide) if there is no item i will try to explain it the best I can. If you would like to help me out please tell me what is in the secret area so I could just viewclass it. Or if it's a secret item. If its in a decoration, please tell me what (i'll be willing to search every barrel and box 
) Anyways here is what I've found over the years (Oh and if you have any cool tips it'd be awesome for you to share 
Vortex2 - None that I know of (unless you consider kevlarsuit secret??)
Nyleve - Tip: Jump off cliff and land safely on land with out diying
Dig - Armor (2)
Superhealth
Small Cave
Dug - ASMD
SuperHealth
Sacred - Superhealth
Chizra - Amplifier
Shieldbelt
Armor
Ceremony - none that I know of
Dark - Address thingy
Superhealth (need help on, question will be at bottom)
Basement
Harobed - Grave
Armor(in church) should it be considered secret?
terraLift - none that i know of (unless you wana count the superhealth?)
Terraniux - Superhealth, ammobox
eightball ammo, shellbox
Noork - Flakcannon
Ruins - Invisibility
Flakcannon
weapon powerup
Shoot picture to make thunder noise
Trench - None that I know of
Isvkran4- ASMD
Isvkran32- Jumpboots + stingerammo + superhealth + eightball ammo
Shieldbelt
Isvdeck- invisibility
superhealth
Spirevillage- attics
Thesunspire - none that I know of
Skycaves - None that I know of
Skytown - Tip: Getting to church, no cheating, no jumpboots, no boosting
Eightball
Fireplace
Skybase - Monkstatues
Tip: Getting to skytown, no cheating, no jumpboots, no boosting
Veloraend - Tip: Lure stone titan to bridge then lower it
Bluff - Superhealth (2)
Armor
Eightball
shieldbelt (not sure)
rifle (not sure)
Dasapass - should I count the shieldbelt in the box?
Dasacellars - superhealth
ASMD
Naliboat - Tip: How to get land near start when in water (no cheats or boost)
lighting picture by shooting torches and the picture in general
ASMD
NaliC - Amplifier
Superhealth
Nalilord - none that I know of
Dcrater - none that I know of (just a cool powershield, not really secret tho
)Extremebeg - None that I know of
Extremelab - Weird secret (see in cheat section)
Superhealth + shieldbelt
Extremecore - Jumpboots + superhealth
Extremegen - None that I know (unless you count all those items scattered out)
Extremedgen - None that I know
Extremeend - I'll count the kevlar and ammo since people might not really notice the doors to 'em :p
Queenend - None that I know of
- Cheating to get to cool places -
Sure everyone knows how cool it is to fly up and explore the mountains, but here are some other cool places people may not notice
opening forcefield to skybase in skytown
in Extremelab ghosting to an odd room with everysingle weapon...
Other: Flying on a book
Picking up a book (command grab with dispersionpistol or automag in hand)
If uou go down a slope fast, you can jump right when you hit the floor (has to be perfect timing) and you do a far jump and if you hold your crouch button and jump again when you hit the floor you can do a far jump again (must be perfect timining) If you get the right speed you can do this an infinite amount of times (in ut 1 you can atleast) This one to me is very cool, yet very useless. It's very easy if you set your jump button to middle mouse down or up. Heres a vid of it (she is transparent because of the gametype)
More to come!
Question on superhealth secret in Dark: I think I know the official way to get it but i'm not positive, do you run and hurry up and jump onto the thing that goes up (you have some time to do so) and then hug the wall and let the titan pound the floor and boost you up?
Thanks for the help guys! :D
I'm really confused as why that really matters? Anyways I know I will definietly need to make videos for some of the stuff. So I'll probably post links on there too.