I would consider the plan of Henry's. This little vent window works great and can be sealed nicely and vent outside.
However, please consider this: many dryer vent force will not carry debris, lint up hill too much. Try to also not create any turns in the line either gradual or not gradual. Lint does build up on the front side of these turns and becomes a blockage in short time. Its like colestrol in the arteries.
If this happens, you are straining your dryer.
As Jay eluded to, dump this stuff out in a professional manner. I have gone into some older homes that do not have exterior dump sites and the lint and debris has been dumping out under the house (peir and beam) and the stuff is a mess. Its also a fire hazzard. Dump it properly.