DJ Earworm is amazing and, if you do not know about him yet, then you are going to be inundated with information on him in the years to come.
He's a DJ (erm..duh?) who finds popular songs, takes them apart, then puts them back together to make these amazing mash-ups that always turn out flawless; the lyrics and notes are lined up so perfectly that his mash-ups are usually better and more enjoyable than the original song (and he does just as great a job on the music videos).
He's done plenty mash-ups of popular songs ("Beautiful Mashup," "Backwards/Forwards," "Love and Wonder," "If I Were A Free Fallin' Boy," "My Life Would Suck Without You In My Place," "Reckoner Lockdown," "Fly," "Heartless in a Bottle," "Mama," and "Like OMG, Baby" to name only a few of his great mash-ups), but his most popular mash-ups may be the series titled "Music For Sport" and "United State of Pop".
"Victory Mix" and "Faster/Stronger" are the two mash-ups from his "Music For Sport" series and they're great. "Victory Mix" has three parts ("Don't Stop Feeling Good," "Gold," and "All Champions Do Is Win") and "Faster/Stronger has four parts ("Bulletproof Titanium," "What Makes You Born To Run," "Speed," and "Power"); they're set up like movements of music, all corresponding to that main theme of "Music For Sport".
Personally, my favorite mash-ups almost always come from his "United State of Pop" series though. He began the series with "United State of Pop 2007" and continued to release these mash-ups yearly, all of which contained the top twenty-five songs on the charts from that year ("Viva La Pop," "Blame It On the Pop," "Don't Stop the Pop," "World Go Boom," and, now, "Shine Brighter").
All of the mash-ups are great and picking a favorite is kind of difficult (and everyone has their own), but I've always played "Blame It On the Pop" (2009), "Fly," "Heartless In a Bottle," and "Don't Stop the Pop" (2010) just a few more times than the other mixes. Of course, now I am completely addicted to "Shine Brighter" (2012), but that's to be expected.
He puts a great amount of work into creating these amazing mash-ups (and their videos) whose individual songs blend together so smoothly that you could never imagine these songs not being made with the initial goal of, someday, working together. DJ Earworm deserves far more credit for his work than other DJ's (such as Deadmau5 or David Guetta) whose music just does not sound as good as these mash-ups.
Keep an eye on DJ Earworm's website to catch all of his new mash-ups (they are always great [and free]) and to read his analysis of each "United State of Pop" movement; he gives a great synopsis of the themes used in that year's popular music.