The site http://prirucka.ujc.cas.cz/ is amazing for learning the declensions of nouns and I found it through this forum. Pity it doesn't handle adjectives in the same manner although it does give the comparative and superlative. Does anyone know a site where one could input a verb and get a list of its different aspects? To my mind, this is more difficult than declining nouns.
I agree: conjugating for aspect is harder than declining nouns. I don't know of any automated service that will do this for you. Nevertheless, aspect is a favorite subject of mine, so I'll take this moment to advertise a guide I put together a while. It's neither comprehensive nor automatic, but it might be helpful. http://eminem.kvalitne.cz/aspect.html
Don't know of anything online. Probably the most useful book is "401 Czech Verbs" by Bruce Davies and Jana Hejduková. See here for more details. Regards Phil