I will get into the lesser known hops as well, just wanted to start out with this little gem. Information below (in blue) gathered from the Hopunion Hop Variety Data sheets.
*photo via Flikr from author michaelstyne
Pedigree: Open pollination of a Fuggle seedling, itself derived from crosses between Fuggle and the Russian hop Serebrianker
Diesease Reaction: Not seriously affected by Prunus necrotic ring-spot virus. Good crown and cone resistances to downy mildew, partly tolerant to Verticillium wilt. Prone to insects, especially aphids.
Aroma: Pleasant, flowery, spicy and citrus. Can have a grapefruit flavor.
Alpha Acids: 4.5 - 7.0% w/w
Beta Acids: 4.5 - 7.0% w/w
Co-Humulene: 33 - 40% of alpha acids
Storage ability: 48 - 52% of alpha acids remaining after six (6) months storage at 20ºC
General Trade Perception: Aroma variety with well-balanced bittering potential. It is the most popular hop with the craft-brewing industry. Few still used by major breweries. Good for dry hopping.
Possible Substitutions: Centennial, Amarillo, possibly Columbus.
Beer Styles: Pale Ale, IPA, Porter, Barley wines
Other Info: Released in 1972 and well established in U. S. industry, and was the first commercial aroma hop developed by the U.S.
If you would like to get an idea of this hop and determine by your own tastebuds I highly recommend you go out and purchase these two commercial examples. Each are American Pale Ales and each showcase the Cascade hop:
Anchor Liberty Ale brewed by Anchor Brewing in San Francisco, California
Sierra Nevada Pale Ale brewed by Sierra Nevada brewing of Chico, California
Typical use: This hop is considered a finishing hop so typical use is for flavor and aroma additions but it can definitely be used as a bittering hop as well. Alpha acids are usually not as high as a typical bittering hop so adjust accordingly to hit your target IBU. When used as a bittering addition the bitterness is not as harsh as Chinook but it is not as mellow as Magnum, it falls somewhere in between which is why it is used in the classic American Pale and India Pale Ale styles. Another great use for the cascade hop is as a dry hop addition. This will add to the aroma and somewhat to perceived flavor. You will get a floral and slightly citrus aroma by doing so.
Style use: As stated above from the Hopunion data this strain of hop is most commonly used in pale ales, IPAs, and barley wines. This should not limit your creativity though try using it in a Pilsner, Amber ale, Brown ale, or even a Belgian wit. It may not be to the BJCP style guidelines for some of those styles but that is what the hobby of homebrewing is all about, experimentation.
Flavor/aroma: You find a lot of hops out there that impart a citrus component. What you get with cascade is the grapefruit area of that spectrum. Along with the grapefruit there is a floral component that blends nicely with the perceived citrus tartness. Never having walked through a grapefruit grove I can only imagine that the aroma that comes from the cascade hop would be like walking through one during full bloom.
Substitutions: If I were to be in a bind and not be able to have any cascade hop on hand I would try to substitute with Centennial hop. This is sometime referred to as a super cascade because it has some of the same characteristics but usually higher in alpha acid content. You will not come out with the exact same result but it will still be a great beer. To me Centennial hops are slightly more floral whereas cascade are slightly more citrusy. You may find conflicting information out there but its just how my nose and taste buds perceive it. The others listed in the Hopunion data would also work for substitutions however I think you would start getting away from your original plan. Amarillo has a very high tangerine component and columbus is a lot more earthy/spicy.