This answer is not complete, but it is a start.
One of the most significant differences is:
Weather models use measurements, whereas climate models do not
Put another way: a weather model is an initial value problem. The initial values that go in are of essential importance for the result to be correct.
A climate model solves what is primarily a boundary value problem. The initial values should not matter. In fact, climate models are "spun up", that means, to determine the climate 2000–2100, the model run may start in 1950 to get rid of initial values. Then, the relevant information is not the weather or March 23, 2063; but the statistics of the weather (mean, standard deviation, etc.), over 2060–2090 (for example).
So if a climate model runs 1900–2100, it is not expected to reproduce the climate for a particular year. This is commonly misunderstood, and might be taken by climate skepticists as showing that climate models don't work (for example, “they don't reproduce the recent lack of significant atmospheric warming!”, not realising that this doesn't matter). Different are analysis or reanalysis (weather) models, that do use measurements, and therefore do represent the weather in a particular year accurately.
As stated before, this is only a partial answer. There are many more important differences, but this is one of the most important ones.