Have you realized how self conscious you become when you are interviewed? The fact that everyone is watching you, critically scrutinizing you can unnerve you and you often stumble for words and make mistakes. Practicing is the best way to improve your communication skills. If you can't find somebody to ask you questions and give feedback, then try InterviewTrue.
InterviewTrue is a website that allows you to take a mock interview of yourself with a virtual interviewer. You set up a webcam, connect to the website and start a mock interview. A virtual interviewer will ask you typical interview questions based on the type of interview you wish to take. The entire interview session is recorded via your webcam.
When the interview is over, you can replay the interview and analyze your communication skills, body language etc. InterviewTrue will also send you a transcript of the interview and you can analyze how many times you have said "umm", "uh", "I mean", "you know" and such filler words. InterviewTrue also offers you helpful advices to improve your interview skills.
Watch some of the webcam recordings of people who took the interview.
P.S: Barack Obama reportedly mumbled "uh" 73 times during a 5 min interview on “Larry King” on CNN.