I highly recommend reading the following books (both from the same author):
- The Google Resume - Gayle Laakmann McDowell (http://www.thegoogleresume.com/)
- How To Crack The Coding Interview - Gayle Laakmann McDowell (http://www.careercup.com/book)
Both are available online (amazon etc) in hard copy and digital.
If you only have time for one, read the former, and peruse the latter. If you find that you are getting interviews but failing to get through the technical questions, you will definitely want to read all of "How To Crack..."
Employers (especially the big name ones) aren't looking for you to get the right answer when they ask you something, and they aren't looking to see that you have great memorization skills either. They want to see your thought process. How do you approach a problem? Can you debug your code? Do you think about what you're writing before you jump in and start making assumptions? Do you ask questions to eliminate ambiguity? Are you cold and focused only on the work at hand, or are you bright, interested, and pleasant to be around (Culture fit)? This is what the interview process is about.
Maybe you aren't saying the right things on your resume. Maybe you aren't highlighting your projects, and you are only highlighting your skills (does your resume read more like a job description than a list of accomplishments?.. Start there).
Some of the other comments mention networking, and that you should have been looking for your job since your freshman year - interning, making connections, and seeing where you are a good fit. The job search doesn't start graduation day. These mistakes could really put you behind the curve. Hopefully you have a good network established that you can tap into. Ask your professors, your old classmates (Have they been hired? Where? What are they doing? How did they make it past the HR nazis? Take a look at their resumes and see why you're not getting any callbacks), talk to recruiters and job placement specialists that your school may have. You have resources all around you that you have built up over the years - utilize them!