This is where I usually find all my Magnets for my magnet collection:
HDD's (hard disks)
Fans (These are round magnets and usually really soft, With that comes the weakness :( )
Regular electric motors
I've also found Magnets inside of a microwaves magnetron, But that is really dangerous and you should only do it if you know what you are doing...
Please contact me if you have another idea for where can you find Magnets!