20) Audubon Guides ($19.99): Yes, it's the most expensive reference guide here, but it's worth it. Enjoy gorgeous color photos and definitive guides to birds, mammals, trees, and wildflowers.
21) Boater's Pocket Reference ($4.99): Whether you're a beginner or a veteran on the high seas, this guide is an essential.
22) Car Factor (free): Save money and shop smart for your next car. This app includes info on 13,500 makes and over 350,000 options.
24) Free Law Dictionary (free): Latin lingo got you frazzled? Look it up in this guide to over 1,200 legal terms.
25) HTML5 Reference Guide (free): A must for site-builders, this guide includes everything you need to know about tags, attributes, and HTML5.
26) iFixit (free): Don't pay someone else: fix it yourself. This attractively-illustrated guide includes step-by-step instructions for thousands of projects.
27) Instrument Flying Handbook ($2.99): Pilots going for their instrument rating will love this handbook, which includes over 1,600 pages of information.
28) The Law Guide (free): When you have a legal question and need some advice, turn to this guide. It includes over 7,500 legal definitions and the full text of many important legal documents.
29) LawStack (free): Better than a stack of law books, this app includes the text of several documents and state codes.
30) Pilot Handbook ($2.99): This ebook offers the full text of the 2008 Federal Aviation Administration's Pilot's Handbook of Aeronautical Knowledge.
31) iSpeak French ($1.99): A must for French travelers, this app translates from English to French and French to English. It also lets you save and mail translations.
32) iSpeak German ($1.99): Hear German words with the correct pronunciation. This app includes a high-quality German voice so you'll always know how to say things.
33) iSpeak Spanish ($1.99): Translate Spanish words and phrases anywhere you go. Note that these and the other iSpeak apps require an Internet connection.
34) iTranslate (free): For the serious world traveler, this app can translate words and phrases in over 50 languages.
35) My World Atlas - Lite (free): More than an atlas, this app lets armchair travelers explore the world and learn about other countries.
36) Spanish Phrasebook with Audio ($.99): If you want to be able to say more than "please" and "thank you" on your visit, this app teaches conversational Spanish.