I'm looking for a 2.1 setup to add to my TV. I'd like my speakers to be as small as possible, and I'd also like to not have to use an external receiver. The Boston Acoustics Digital Cinema speaker set is a good example of this, but I'd like to see what my other options are. Thanks!
You aren't going to find much that will compete with that system price-wise.
The real problem with that kind of system is mid-bass - a 2.5" "woofer" just cannot physically recreate bass down to the upper frequencies of the sub - so you are left with a hole in the mid-bass. Same reason that Bose "cubes" sound so bad - they are fine when there is a special demo playing with highs and sub content, but just try to understand male voices through those things. I wouldn't recommend any "woofer" below 4 - 5" unless the speaker has multiple woofers to make up for the small size - that is going to give you a speaker size of at least 6" wide and 9" tall.
Regular speakers would require an external amplifier, so I would suggest powered speakers and a powered sub. You won't need an external receiver, but you WILL need a variable audio output on your TV - I had to specifically look for one that had it. Look at some of the small powered speakers from Paradigm, M-Audio, AudioEngine, PSB, etc and pair that with a budget Polk sub from Amazon.
I have the M Audio AV40's hooked up to mine and they sound 100 times better than the TV speakers even without a sub, but they are not tiny speakers - 8.75" (H) x 6" (W). I also use the front input to listen to my MP3's when I'm in that room and want music.