I'll limit myself to the ten best albums I've downloaded this year since I tend to focus on previous years (in no particular order):
Death From Above 1979 - You're a Woman, I'm a Machine (2004)
I'm pretty sure this band's sound is my tastes in a nutshell: a two-piece noise rock band that features a bass instead of a guitar. It's full of repetitive riffs and it's hella catchy. 'Go Home, Get Down' is the standout here.
Defiance, Ohio - Share What Ya Got (2003)
I heard 'Hey Kathleen Are You Hungry?' randomly on youtube and absolutely loved it. Yet, it took me a while to download the whole thing because I was unsure I would like this folk punk stuff. Boy, was I wrong. Now they are the fifth most played band on my last.fm, essentially because of this record. 'Road Signs Always Look Better Over Your Shoulder' is my favorite now, but it seems like every song is a favorite and that it changes weekly.
Japanther - Skuff Up Your Huffy (2007)
Another album that really fits me. Japanther is just about the best at combining noise and pop, and this is by far their best album; it's a great listen. '$100 Cover' should be everybody's favorite, it's beautiful.
Refused - The Shape of Punk to Come (1997)
Most of you are fully aware of this album. I was skeptical at first because I had heard it included a lot of experimentation, but this album truly is perfect, with just the right mix of poppy singles and extended prog punk type songs. My favorite is 'Summerholidays vs. Punkroutine'.
Super Furry Animals - Radiator (1997)
I can thank Urban for this awesome album. I had heard bits of two of their more recent material, but he was right; this is there magnum opus. I like 'She's Got Spies' the best for the part when it explodes with energy.
Test Icicles - For Screening Purposes Only (2006)
I kinda listened to this album on a whim after hearing 'Boa vs Python'. They had a cool sound and it's too bad they disbanded.
Elastica - Elastica (1995)
I heard this one over the summer and loved it right away. Every song is quick and catchy--exactly the way I like it. The hit, 'Stutter' was the first one I heard and still an alt classic to my ears.
Outkast - Stankonia (2000)
What was essentially the first hip-hop album I downloaded. Plenty of good songs outside of the radio hits--'Humble Mumble' is especially a favorite of mine.
Japandroids - Post-Nothing (2009)
I downloaded this album last year but didn't get around to listening to it until a month ago. Why did I wait? Yet another awesome two-piece. 'Crazy/Forever' is my favorite.
Nas - Illmatic (1994)
Up there with the best hip-hop I have heard, although it took me a little while to get into. The album stays strong from start to finish. You can't go wrong with 'New York State of Mind'.