As a college consultant, I am frequently asked about college guidebooks and SAT / ACT prep.
COLLEGE GUIDEBOOKS:
There are many good college guides, but my personal favorite is Fiske Guide to Colleges 2011, 27E The Fiske Guide includes the colleges and universities that most typical high school students consider.  In addition to providing an easy-to-read review and summary for each school, Fiske rates each college’s academics, social life, and quality of life on a scale of 1 to 5.
SAT & ACT PREP:
Strong entrance exam scores improve chances of acceptance and can also lead to significant scholarship money. The SAT and ACT are very different college entrance exams. Most colleges accept either (or both). The tests have distinct personalities — the ACT is curriculum-based, while the SAT is more of a general reasoning and problem-solving exam.  ACT questions are  more straight-forward, and students who score well tend to be fast readers, with strong memorization and information processing skills.  In contrast, the SAT focuses more on reasoning, and students who achieve high scores tend to be avid readers, with strong vocabularies, who enjoy test-taking strategies and nuances. The Princeton Review’s ACT or SAT?: Choosing the Right Exam For You (College Admissions Guides) can help you evaluate your options.  Many students take both exams.
These are two essential prep books:

• Official SAT Study Guide
• The Real ACT Prep Guide

Grammar is important for the ACT. Etymology is especially helpful for the SAT.

• Painless Grammar (especially helpful for ACT)
• Word Power Made Easy (Etymology – understanding word roots and origins, extremely useful for SAT)

Preparation is a proven method to improve scores on both the ACT and SAT.  Here are some additional suggestions:

• Kaplan’s SAT Score Raising Classics such as Dr. Jekyll and Mr. Hyde, Frankenstein, War of the Worlds, and Tales of Edgar Allan Poe.
• SAT Dictionary
• Quizlet.com
• Brightstorm Test Prep (online programs for SAT and ACT)
• SparkNotes Test Prep and 250 Most Difficult SAT Words (Free)
• Berkeley Parents Network Vocabulary List (Free)
• Vocabulary Cartoons: SAT Word Power
• Essential SAT Vocabulary (flashcards) (College Test Preparation)
• Kaplan SAT 2011: Strategies, Practice, and Review
• Increase Your Score In 3 Minutes A Day: ACT Reading
• Increase Your Score in 3 Minutes a Day: SAT Essay
• Increase Your Score in 3 Minutes a Day: SAT Critical Reading
• Official SAT Question of the Day from The College Board (Free)
• Number2.com Question of the Day (Free)

Finally, if you are seeking good general advice, check out:
You’re Accepted: Lose the Stress. Discover Yourself. Get into the College That’s Right for You.