Resources Every Chemist Should Have

A brief excursion to show you all some of the tools I think that every organic chemist (or chemist) should have.  I will list some textbooks, as well as online resources that are great references.

Textbooks:

1.) Organic Chemistry - Clayden (link)
This is a wonderful textbook that for an introductory organic chemistry book, is very detailed.  By far the best text out there.  Covers a large scope of reactions in sufficient detail so that one can gain a very in depth understanding.
2.) Advanced Organic Chemistry Parts A&B - Carey (Part A) (Part B)
These should be your second books that you read on your trip to understanding organic chemistry.  Part A is a more in depth look at mechanisms, Part B looks into learning a bunch of reactions.  To extend and diversify you reaction knowledge, these books are classics.
3.) Modern Physical Organic Chemistry - Anslyn (link)
This book solidifies your understanding of why reactions happen and give you the most in depth and fundamental understanding to all sorts of reactions.  It emphasizes applying thermodynamics and kinetics to all parts of organic chemistry and helps one to use these fundamentals to explain just about everything.  This book is my all time favorite.  Extremely well written, easy to follow, and it is not riddled with equations like most physical chemistry books are.
4.) March's Advanced Organic Chemistry - March (link)
This book is really more of a general reference more than something you would actually read though.  It's filled with so many references you wouldn't believe!  If you are performing research and are looking to learn more about a particular reaction, this is where you should go.
5.) Greene's Protective Groups in Organic Chemistry - Greene (link)
Another reference book and not something to read through.  But like the title says, if you want to protect something, this is where you go.  There are some great tables in the back that show you around 50 conditions that you could apply to your protecting group, and it will tell you if it is stable or not.  Excellent reference, and another classic.
6.) The Art of Writing Reasonable Organic Reaction Mechanisms - Grossman (link)
If you want to be able to predict mechanisms or brush up on your skills to diversify what mechanisms you can describe, this is a great book.  Like the title says, you will be able to better predict what electron pushing mechanisms are most reasonable to predict what products are most likely to form.

Online Resources:

1.) NMR Chemical Shifts (link)
What a great link this is!  Shows you a wide variety of proton chemical shifts for like a bazillion functional groups with many relevant examples of each.  A gold mine if you are curious about where a new functional group should appear.  Also, clicking the home page link in the upper left hand corner takes you to the home page where you can find even more resources!
2.) pKa Table (link) and for Heterocycles (link)
Here are the pKa's of a variety of different functional compounds from where you can predict how acidic something is.  This is the broadest table I have seen and it has been very useful so far.  The second link specializes for some common heterocycles.
3.) Bond Energies (link)
If you want to get a rough idea of how favorable your reaction is, a very simple way to rationalize things are with bond energies.  This is a table that shows you how strong bonds are.  If your products contain higher bond energies, they have stronger bonds, then they are thermodynamically stable, and likely to form.
4.) Elemental Properties (link)
Here you can find any physical property you want for you molecule.  Constants such as Young's modulus, enthalpy of formation, standard entropies, heat of fusion, etc.  You name it, this site has it.

*Note: The best way to find the property you want, is to click on the element you want to learn about (for bond energies, you can click on either element in the bond) and then to look for the link on the right panel that says "Find a Property".  From here, click on the property you want.  The left column defines the property, but the right hand column shows the actual physical data.
5.) Encyclopedia of Reagents for Organic Synthesis† (link) 
This reference lists properties and common uses of tons of different reagents.  So if you are curious about why a reagent is used, or in what reactions it is used, an excellent reference.  I use it frequently in my posts.
6.) Rules for Predicting UV Absorbance (link)
If you want to predict how UV spectra change upon changes in an aromatic system, this website has the rules.  Woodward actually helped to empirically determine these rules :)
7.) What to Dry Solvents With (link)
If you need a dry solvent but are not sure of reagents that are compatible, or what is the best way to dry it, this website has a table with the popular ways to dry a wide variety of common lab chemicals.
8.) Solubilities (link1) (link2)
If you need to know the solubility of a substance, these two links are good places to look.  They give accurate information about the solubility of a substance.  The first link is most easily searched through the google doc on the first page.  The second link works best when searching by CAS number.  Excellent reference I think, and this data should be more available.
9.) Reaction Finder (link1) (link2)
If you want to know what a particular reaction is or what it involves or even if it has a name, these next two links are useful for identifying, but perhaps not for learning more about it.
10.) Journal Abbreviations (link1)
A search engine where you can search from abbreviation to the journal name, or vice versa.
11.) Functional Group References† (link)
The page hosts links to common chemistries of a variety of functional groups.  Very useful if you want to learn more about chemistry of one particular functional group.
12.) Organic Syntheses (link)
A entire collection of the detailed reaction and workup procedures for a variety of compounds.  For me, I just enjoy browsing through these from time to time to learn more about the workup procedures, and to understand what each step in the work up accomplishes.
13.) Organic Reactions† (link)
It gives great detail about the mechanism, side reactions, etc.  To fully utilize this resource, you can navigate the book from the left toolbar, where you can search by structure, title, or reaction type.
14.) Merck Index† (link)
This index is a classic.  So many properties and references of a variety of compounds including their melting points, descriptions, properties, and often solubilities as well.
15.) Reaxys† (link)
An alternative to the popular Sci-Finder reaction search, you can search a reaction or even a structure to search for actual procedures for the reaction, or procedures to synthesize a compound.  Provides references to the actual papers used, just like Sci-Finder.

† = academic access needed