This magnet is hilarious and my toddler LOVES it - http://www.amazon.com/LeapFrog-Fridge-Farm-Magnetic-Animal/dp/B0001X0DR6/ref=sr_1_1?ie=UTF8&qid=1345209002&sr=8-1&keywords=barn+magnet
We don't have many toys that talk and sing, but this one is great and would be a fun addition to your wall.

We have the farm set by Shure, they make lots of other sets and they are really cute!
http://www.amazon.com/Shure-9200-Farm-MagnaWheels/dp/B000OQOSH6/ref=pd_sim_t_3

LeapFrog Fridge Phonics http://goo.gl/TBQ0N

we are just doing the same thing this week! we bought magnetic primer, but then returned it and bought sheet metal from a local contractor, as it was almost the same price. i want this: http://www.bernhard-burkard.com/index.php?/projects/plama--marble-run-2d/. but i will probably settle for frigits or something less expensive.

I bought a US map puzzle and plan on placing adhesive magnet backings on each piece for our magnet board.

also, have them pick out a magnet from the souvenir shop at any place you visit

My little girl loves these dinosaurs magnets : http://www.melissaanddoug.com/wooden-dinosaur-magnets

Our fridge is a magnetic toy mess! We do have the large magnetic letters and our 3 year old is very interested in putting together strings of letters and asking us to "read" her word. We love these magnetic stacking acrobats and even adults enjoy playing with them http://www.giggle.com/on/demandware.store/Sites-giggle-Site/default/Product-Show?pid=0004086431&gclid=CPbLifz-7rECFQkaQgodbnMAZg
We also have these magnetic gears and even the 10 month old plays with them http://www.constructiveplaythings.com/cgi-bin/s.sh/2.0/product.htm?pf_id=CYI-30
I would love to add one of these magnetic puzzles to the collection once the baby is beyond the choking on things stage http://thewoodenwagon.com/woodentoy/NA/GSH91167.html

We have the Tomy set, which is popular with my toddler and anyone visiting, but it's only five pieces and the toddler is convinced that one of the pieces should not be used and banishes it under the fridge. I think I may have to order the Magnetic Gears as a supplement. (The Tomy pieces are a bit more interesting...)

the djeco brand is also really cute and creative. here is an example...http://www.amazon.com/Djeco-Wooden-Magnet-Crazy-Animals/dp/B000VIYCTG

These are amazing and bring hours of fun:

http://www.amazon.com/Magna-Tiles-Clear-Colors-piece-set/dp/B000CBSNKQ/ref=sr_1_1?ie=UTF8&qid=1345370339&sr=8-1&keywords=magnatiles

Also we have the Melissa and Doug ones which my little one likes:

http://www.amazon.com/Melissa-Doug-Animal-Magnets-Box/dp/B000N178E2/ref=sr_1_1?s=toys-and-games&ie=UTF8&qid=1345370414&sr=1-1&keywords=magnets

I would recommend the Mudpuppy magnetic shapes magnets. They made letters, numbers, fruits and vegatables, and farm animals. I have a two year old and we have the letters, numbers and fruits and veggies and she loves them all. We also have the Leap Frog fridge farm, which she liked more when she was younger, but still plays with from time to time.

My kids absolutely love these Q-Man magnets!
http://www.vat19.com/dvds/q-man-mini-flexible-magnets.cfm

i second magnatiles http://www.magnatiles.com/

also Moma Magnetic Alphabet Set by Arun Kumar H.G., 2005http://www.momastore.org/museum/moma/ProductDisplay_Magnetic%20Alphabet%20Set_10451_10001_45951_-1_26698_26700_45952

Frigits are cool too http://www.funkyfridge.com/TH-6222.html