I was just asked to perform Mentalism for 45 minutes at a large conference of about 1000. Any ideas on effects? Needs to be fast paced with little set up or preshow.

You agreed to do 45 minutes in front of 1000 people and you don't already have a show?
I really don't mean to be rude, but if you are here asking about effects, I don't think you should be doing the gig....

The show must go on. Let's begin with what you're used to.

1) What length and audience size are you accustomed to performing for?

2) What kinds of routines are you comfortable with under those circumstances?

I don't think there is too much of a difference between 100 and 1000 people, in terms of usable effects..
You should just do your standard stage material!

What is the date of the performance and what material do you already have practiced and ready to go?

Any jumbo tron?

I totally agree with Mr laugh. This is the worst thing you can do for your prospective client. What you should do is tell him you are booked but next time you will offer him a free show for his review.

Other than that I'd recommend the psychic egg bag.

Everytime I describe my show and tell them what I'm doing, they say it's too small. I'm wondering if I'm missing some larger scale effects. 4dt, blindfold, q and a, I thought would all work, however they want larger visuals such as illusions. They also can't guarantee a projector.

And before I get any other smart guys asking you agreed to this without a show? I have a show, I do this for a living. They just doubled the audience size. Can I quit and run and hide? Yes. But this is how I make my money. So rather than being rude. Try addressing the original question, are there any visual larger scale effects?

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Lior

In terms of something visual that takes up the performance area, there's always a chair test.

Okay no offense meant. The phrasing of your original post made me think you didn't have a show. Apologies.

I only mean to say I don't think trying new stuff that you haven't already honed in front of a very large audience seems like the best idea to me. If it's stuff you have done in the past, then, that's a different story. And I certainly understand not wanted to turn down a gig.

Personally I have no experience with audiences larger than a few hundred, but I think that without the projector, I can think of a few things that could help.

Using your participants as your props is a good direction.
I would imagine a chair test is good, also maybe a kurutsoke or Body Language type effect
How about Ken Dyne's effect E1. It uses a banner.
Use a flip chart and jumbo marker instead of a pad for your revelations.
A prediction (using a force) that is revealed in a large scale.
Q and A seems like a great idea since it potentially involves the whole audience. I would think that is a great way to keep everyone's attention.

Things that fill the stage can be a simple as a black board of the types we had in school The chair test already suggested. Sudo hypnosis or psychokinetic touches. Kurotsuke will get 5 or 6 people on stage. Just anything that fills the stage.

Having said all that, it's YOU that must fill the stage with your charisma. Nothing else is as important.

I wish you well and I hope you raise your price for this show. I'd be pretty upset if someone double the audience on me without proper compensation.

I perform the same show for 20 people that I perform for 1000 people. The biggest venue I've performed in was the 4000 seater plymouth pavillions. The main difference, I write on a bigger pad. For visual effects a chair test with 5 people on stage is perfect.
If you've already got a show, you'll be fine, just think bigger props. It sounds like they know what you perform so if they want illusions it's on them for booking a mentalist.

Thereyago!

"Kurutsuki," already mentioned, is great.
Also, Banachek's "Telekinetic Touch."
Becker's "Serial Killer."
"Magic Square" on a large dry-erase board.
"Which Hand," with several spectators, narrowing down to one.

Sounds like your client does not understand what is possible in a larger venue and assumes that an illusion show is required. Derren Brown and David Berglas before him clearly show that mentalism can be done in large venues. Colin Cloud's performance as The Deductionist in The Illusionists touring show is a more recent example as are his performances on AGT. They key in every case is to involve large numbers of various audience members. Use the entire stage and the audience as your props. As always, choose participants that will react very visually since they cue the audience. And perhaps most important, be sure to get advance rehearsal time in the venue, including a technical rehearsal.

Jstreiff has hit the nail on the head!

People like Derren, Colin, Keith Barry and others have demonstrated that mentalism can be done with minimal props in a larger venue.
But to best demonstrate this you can use effects that will get large numbers of people involved at any one time such as a Kurutsoke effect (Mr Golden Balls maybe), Chair tests, E1 by Ken Dyne, use big pads and a jumbo marker, and just effects that will leave a stunning visual (one of the most powerful effect's I've ever seen was Derren's version of Koran's Gold Medallion effect)

Another piece of advice I can suggest is maybe to have some form of backdrop (even if its just projected onto the back wall) and it gives the impression that there's more going on

This is probably too late for your show, but for future reference, the excellent Marc Paul Penguin Lecture has a number of very entertaining effects which use a number of people and would look very good on a large stage. In general, he gives great advice on how 'ordinary' effects can be tweaked with some imagination to play larger by using people in them in a different way.
He has an interesting opener using numbers left on the stage prior to his entrance which will also involve lots of people before you even start.
Highly recommended indeed.

Very best,
Francis