Bad toaster or bad wires?

One cause for a blown fuse (or tripped breaker) is a short circuit. That means that an appliance plugged into that circuit is damaged, or it could mean that the wires in that circuit are damaged.
To determine if the problem is a damaged appliance, unplug everything on that circuit and see if the breaker will reset (or see if the replacement fuse holds). If the breaker will reset, the problem is in an appliance. If it won´t reset, the problem is in the wiring.
Whatever the problem, do not use the appliance (or circuit) until repairs have been made.
Also, see the categories Grounding, and Safety.

Too many appliances

One cause for a blown fuse (or tripped breaker) is an overloaded circuit. For example, when you turn on your microwave, coffee pot, and toaster at the same time, the breaker trips.
The outlets in most modern kitchens are divided into two circuits, each rated at 20 amps. Try moving one or two of the appliances to the other side of the kitchen, to the other circuit.
Also, see the related tip categories of MICROWAVES, and That Funny Outlet With The Reset Button.