So - partly so that I have an easy record of sources to access, and partly in the hopes that all this might be helpful to someone reading this someday - here are a number of the online resources I've found to be a great help at this point in my study. (I've enough basic knowledge of Spanish to often (but not always) be able to figure out a word's meaning using a Spanish-to-Spanish dictionary. So I don't know what sorts of resources would be most useful to someone starting from scratch).
Tools
I've been using Mnemosyne, and Anki is another common one. One thing I really don't like about Mnemosyne, though, is that I can't shuffle the cards. (Maybe I've just missed the checkbox on the options menu?). But I don't know if Anki is any better when it comes to shuffling.
This is holy grail of Spanish online dictionaries. I've looked at several other online dictionaries and translators, and none of them can hold a candle to this site. It's miles ahead of anything else I've seen out there in both ease of use and thoroughness of definitions.
Both of the dictionaries are very good at noting idioms, showing which prepositions go with what verbs, and giving example sentences. Moreover, they do an excellent job identifying the verb you're looking for whenever you type in a conjugated form. Which is an absolute lifesaver when one runs into an unknown irregular form, or isn't even sure that the word they're looking at is actually a verb.
Also, they're so, so, so much faster than flipping through a dead-tree dictionary. And they're especially useful if one is using a computer flashcard program to keep track of words and sentences.
Audio
Although I'm somewhat wary of mixing European Spanish in with Latin American at this point...I do very much like RTVE (the Spanish version of NPR, as far as I can tell). It's a rather classy series of stations all around, with few commercials and high sound quality. Channel 1 is news; channel 5 is a wide variety of programs, including interviews and talk shows.
Video
The only TV shows I've found that come from Latin America are horribly cruddy low-budget soap operas. Which is a shame, because shows are a rather good way of learning to comprehend oral Spanish. However, if you're willing to toss some European-style Spanish into the mix, do check out the Amar en Tiempos Revueltos. It's something of a historical melodrama (historical soap opera?), set in the years surrounding Franco's dictatorship. So there's fights and politics and death, and far grander conflicts and betrayals than mere romantic ones. It's also got excellent production values - crisp filming, intricate period costuming, and I'm assuming good acting (though that's rather hard to tell when I understand only 5% of what they're saying, at best). What I've seen of it, I very much like.