thehoodinternet.com is a website that mixes alternative favorites with rap/hip hop songs.
They (I believe the company consists of two guys that run the site and do the mixes) take big names in alternative rock such as Spoon, the Shins, Modest Mouse, Rilo Kiley, The Go Team!, the Yeah Yeah Yeahs, etc. and combine them with rap industry big whigs like Notorious B.I.G. (RIP), Jay-Z, Kanye West (!), Lil' Kim, Missy, the Clipse, Ghostface, etc. There are also more obscure artists featured in both genres, if that's your thing.
These particular mixes differ from their inferior counterparts in that they are actually thoughtful and artistically melded...each track is done individually so it's not just both songs playing over one another.
The website offers its most recent downloadable mix-tape here.
2. The Pack vs Crystal Castles | I'm Shinin' Like A Crystal
3. Dizzee Rascal vs Cyndi Lauper | Girls Just Wanna Fix Up
4. Rhymefest vs !!! | Put It On My Chk Chk Chk
5. Rick Ross vs CSS | Push It To The Alalimit
6. Birdman & Lil Wayne vs Black Rock | Stuntin' Like Black Rock
*7. Rihanna (feat. Jay-Z) vs Menomena vs M83 | Cyborg Umbrella
8. Trillville (feat. Cutty) vs The Knife | Some Cut Like A Knife
9. Omarion vs Mylo | Drop The Icebox Pressure
10. Tag Team vs LCD Soundystem | Great! There It Is
*11. Lloyd vs Feist | My Moon My Shawty
*12. Crime Mob (feat. Lil Scrappy) vs The Shins | Rock Yo Sea Legs
13. Swizz Beats vs Deerhoof | It's E.S.P., Bitches
*14. Lil Wayne vs Modest Mouse | Fire It Up, Firemouse
15. Lil Mama vs Marnie Stern | Absorb The Lip Gloss
16. Mos Def vs Battles | B-Boy Battles
*17. The Game (feat. Kanye West) vs The Go! Team | Wouldn't Grip Far
*18. Snoop Dogg (feat. R. Kelly) vs Architecture In Helsinki | That's That Whirlwind
19. T.I. vs Fujiya & Miyagi | What You Know About Transparent Things
*20. TLC vs Led Zeppelin | All My Scrubs
21. Timbaland (feat. Nelly Furtado, Justin Timberlake) vs Hot Chip | Give It To My Boy From School
22. Destiny's Child vs Justice | Lose My Waters Of Naza(b)reath
*23. Ghostface Killah (feat. Jacki-O) vs Spoon | The Ghostface Of You Lingers
24. Khia vs Dan Deacon | Snatch Da Crystal Cat Back
25. R. Kelly (feat. T-Pain, T.I.) vs Broken Social Scene | I'm A Flirt (Shoreline)
26. UNK vs LCD Soundsystem | North America Walk It Out (UNK Soundsystem)
the starred ones are my personal favorites.
There's plenty more where those came from, so check the site out at thehoodinternet.com for new mixes every week.