GREAT topic!
For me growing up through the British Invasion etc. there are many.
Not so much the "obvious" Beatles, Stones songs, but rather those
songs that remain with me and will forever.
The songs I am listing (and I'm sure there will be additions)
are those that have that "timestamp", that indelible mark
left in my brain that as soon as those first few notes, a chorus
or a lyric is heard, transports me to that time, that feeling, that
person or that emotion immediatley.
Funny, as I had this converstion with my 9 year old daughter this past
week (who has been raised with a fine taste in music) of how
the songs she hears growing up will always be associated with a time,
a place etc.
I'll span about a decade and a half or so...
I started the active club, live music scence in Chicago about '73-'74
so it really gets "memorable" )or lack thereof) from then on...
but these came into mind right away.
Thanks for all the great "talk" we have here.
"Boris"

In no particular order (except one)

"I Saw Her Again Last Night"- Mama and Papas
"Summer In The City"- Lovin' Spoonful
"Bernadette"- Four Tops
"Him Or Me"- Paul Revere and the Raiders
"Try Too Hard" - Dave Clark Five
"Out Of Time" - Rolling Stones
"California Nights"- Leslie Gore
"Maybe I Know" - Leslie Gore
"Pleasant Valley Sunday" - The Monkees
"Lay Down" (Candles In The Rain) - Meleanie
"Go Back" -  Crabby Appleton
"Beach Baby" - First Class
"I'll Be Around" - The Spinners
"Long Cool Woman"- The Hollies
"Waterloo" - ABBA
"Right Time Of The Night"- Jennifer Warnes
"Go All The Way" - Raspberries
"I Wanna Be With You"- Raspberries
"Baby Blue" - Badfinger
"Eighteen"- Alice Cooper
"You Got Me Anyway"- Sutherland Brothers and Quiver

....and the Number One Song
that transports me back and haunted me for decades
until the first Nuggets LP was released is...

"My World Fell Down" by Saggitarius

I remember being a kid on vacation in Twin Lakes, WI.
pulling in WLS from home in Chicago and hearing that song in the
Summer of '67...amazing.
Even now it brings back such great, great memories.
This music will forever keep us young.
(Hmmm...2 Leslie Gore and 2 Raspberries)
"Boris"

NP-"My World Fell Down" by Saggitarius
Ahhhhhhhhhhh...
(as the sun sets I can hear them calling out to us
to bring the little kids back in from the beach)