How about the series of calls in Wall Street when the Anacott Steel news hits with Stone going to the split screen.

How about "show me the money" in Jerry Maguire?

When Harry Met Sally, discussing Casablanca over the phone.

Two ringing phones come to mind: the beginning of Once Upon a Time in America and the end of Cellular. But that might be a different week.

How about the recent but oh-so-cool monologue of icy fury by Liam Neeson in "Taken":

"I don't know who you are. I don't know what you want. If you are looking for ransom, I can tell you I don't have money. But what I do have are a very particular set of skills; skills I have acquired over a very long career. Skills that make me a nightmare for people like you. If you let my daughter go now, that'll be the end of it. I will not look for you, I will not pursue you. But if you don't, I will look for you, I will find you, and I WILL KILL YOU."

http://www.youtube.com/watch?v=5Y_Wu36wIEM&feature=related

Doris and Rock in Pillow Talk!

http://www.youtube.com/watch?v=OhxDNtD2hdw

"Have you checked the children?"

The calls from WHEN A STRANGER CALLS (1979)
http://www.imdb.com/title/tt0080130/ ... the original, not the remake ...

the kicker:

Jill Johnson: [thinking it's Curt again] Leave me alone!

Sgt. Sacker: Jill, this is sergeant Sacker. Listen to me. We've traced the call... it's coming from inside the house. Now a squad car's coming over there right now, just get out of that house!

Hey, this theme is turning out to be a great one. Look at the range of phone calls -- horror, comedy, thriller, action. Keep the suggestions coming!

Sleepless in Seattle is loaded with phone conversations, of course. I don't remember it well enough to suggest one in particular, though.

I liked the scene in Silence of the Lambs where there is no dialogue - after Lecter escapes, there's a shot of Starling's room mate dashing down the hallway with the phone hanging off the hook in the foreground.

The Departed has a lot of phone conversations, too.

Patrick Sweeney
I Blame Ninjas

The Graduate:
Ben calls Mrs. Robinson who is in the lounge from the lobby of the hotel in which they are to have an affair.

"Ben, isn't there something you want to tell me?"
"I just want to say I really appreciate this."
"The number."
"What."
"The room number, Ben. I think you ought to tell me that."

My mind keeps going to comedy--

High Anxiety:

Mel Brooks is strangled while on the phone with Madeline Kahn who mistakes him for an obscene caller.

The Matrix (Neo dashing between cubicles on his cell phone)

Tim Robbins talking to Greta Scacchi on his cell while lurking outside her window in THE PLAYER.

The slow zoom-in to Robert Redford on the phone with a source as he puts together the pieces in ALL THE PRESIDENT'S MEN.

Oh, and of course there's SORRY WRONG NUMBER.

Danny DeVito's response to a wrong number caller in "Ruthless People" -- http://www.youtube.com/watch?v=_mj41gYRyw8

"I love wrong numbers" - DD

Here's a hilarious one from "Dr. Strangelove." The President speaking with Russian leader:

I'm Fine Dimitri

Colin Farrel in Phone Booth has some good stuff. And of course Allen (Philip Seymour Hoffman) in Happiness.

There are some great ones in "Almost Famous" between Lester Bangs (Philip Seymour Hoffman) and William Miller (Patrick Fugit) and Ben Fong Torres & William Miller.

One more from "Almost Famous"... Russell (Billy Crudup) and Penny Lane (Kate Hudson) at the end of the movie...

Airplane: (Captain Oveur is on the phone with the Mayo Clinic]

Operator: "Excuse me, Captain Oveur, but I have an emergency call on line 5 from a Mr. Hamm."

Captain Oveur: "Alright, give me a Hamm on 5, hold the Mayo."

i second the when harry met sally call and scream.
I actually saw a good phone moment last night. it wasn't the call but what was going on around. Finally catching up on Nurse Jackie off my tivo. i liked it because it wasn't all clean and tidy and everyone gets their chance to speak like you see in some calls. http://www.youtube.com/watch?v=kcA2dgX5rEQ