If you've looked for GRE videos online, you've undoubtedly come across Magoosh GRE videos. The site offers videos on nearly every possible GRE topic, along with lots of practice questions, vocabulary flashcards, math formula sheets, and other GRE-related info. Magoosh GRE has an active blog with hundreds of articles about the GRE, including lots of GRE vocabulary articles. You can sign up for a one month plan for $79, or a six-month plan for $99.
There is a lot to like about Magoosh's GRE video course. There is a ton of information on their site - a lot of it is free - and the quality is good, in general. But as a GRE tutor who reviews a lot more prep material than the average test-taker, there are several things I don't like about Magoosh GRE that most people may not consider.
Despite all the flaws I've mentioned in my review, Magoosh is actually a good product... when weighed against the GRE prep industry as a whole. If you use it as directed, I'm sure it will help you, and if you'd rather watch videos than read a book, I would recommend it, with the following 5 caveats:
1. Check out my 77 Things To Do During Your GRE Prep blog for a complete list of everything you should do during your GRE prep.
2. Remember, watching videos is not a substitute for working through GRE questions from scratch. Magoosh questions are not as complex or challenging as real ETS GRE questions.
3. Force yourself to analyze ETS problems; don't just rely on the Magoosh answer explanations. You need to be able to explain problems in your words, not just follow someone else's explanation.
4. Give yourself several months, since watching videos is a lot slower than reading a book.
5. You're using a one-size-fits-all course; be open to adjusting techniques if they don't work for you.
Update: I am now a competitor to the Magoosh GRE video course: LinkedIn / Lynda.com just published my complete GRE video course, so you should take my review of Magoosh's GRE course with a grain of salt. :) But I seriously think my GRE video course is worth considering for a couple of reasons.
The one big difference between my course and Magoosh's course is that I only provide practice questions for math concepts. Magoosh provides them for math and verbal, and attempts to write questions in the GRE's style. For math, this can help you get up to speed with concepts, but for verbal, I'd avoid Magoosh questions and only use ETS questions. And of course, make sure you eventually can do the ETS math questions as well.
A general warning: third-party-written GRE questions invariably don't play by the same rules the real GRE's will. This can make you develop bad habits, introduce confusion, and in general, prepare inadequately for the real test. Magoosh's GRE questions are sometimes harder than the real GRE's (for the wrong reasons, which doesn't help) and easier (which obviously doesn't help).
If you're interested in a GRE video course, you can check out my course here on Lynda.com. Here are a couple of sample videos for you from the course demonstrating some aspects of quantitative comparison technique and sentence equivalence technique.
Quantitative Comparison GRE video
Sentence Equivalence GRE video
I have all my GRE verbal and math technique videos on YouTube for free, as well! Check them out once you're ready to practice with official GRE material.
Since it's pretty hard to find a completely unbiased opinion on what material to use for GRE prep, I always advise that people shop around. Wait until you have more information if you're not sure about your decision about what materials or course of study to pursue. And realize that the consensus about certain products is often not very informed. Many reviews are written by people who have only used one or two GRE products and who therefore don't have a very broad perspective. This can create a vicious cycle of low-information, since the more good reviews from inexperienced GRE studiers a product gets, the better it can seem. Try to also find reviews from multiple people who are experts in the field - once you read some of their thoughts, you'll have a more balanced view.
The time you spend on the front end regarding developing a smart GRE study plan will be well worth it in the long run. Don't give in to the tendency to make decisions too quickly when you're new to this stuff. Good luck, and happy GRE studying!