There are several resources for referring to different tables.  The most useful that I have found is Victoria Yudin.  I recommend that you check out her references.

Another resource that I have used is the Dynamic GP Table Reference.  This site is consistently updating the tables and is an excellent resource.  I use it daily. It also has a more robust list for uncommon tables and also has table references for 3rd party applications, such as Wennsoft, Olympic Project Cost, Etc.

Here is my list of common tables I use most often.  They are not a complete list.  If you need a complete list of all tables I recommend visiting Dynamic GP Table Reference.

Financial Batch Tables
GL10000              Transaction Work
GL10101               Quick Journal Amounts Work
GL20000              Year-to-Date Transaction Open
GL30000              Account Transaction History

Budget Transaction Tables
GL12000               Budget Transaction Work
GL32000               Budget Transaction History

Purchase Order Processing Batch
POP10100            Purchase Order Work
POP30100            Purchase Order History

Purchase Order Processing Batch Line Detail
POP10110            Purchase Order Line
POP30110            Purchase Order Line History

Purchase Order Processing Receipt Batch
POP10300            Purchasing Receipt Work
POP30300            Purchasing Receipt History

Purchase Order Processing Receipt Batch Line Detail
POP10310            Purchasing Receipt Line
POP30310            Purchasing Receipt Line History

Purchase Order Requisition
POP10200            POP Requisition
POP30200            POP Requisition History

Purchase Order Requisition Line Detail
POP10210            POP Requisition Line
POP30210            POP Requisition Line History

Purchase Transaction Batch Tables
PM10000            PM Transaction Work
PM20000            PM Transaction Open
PM30200            PM Paid Transaction History

Purchase Transaction Distribution Batch Tables
PM10100             PM Distribution Work/Open
PM20200             PM Distribution Open Temporary File
PM30600             PM Distribution History File

Apply To Tables
PM10200             PM Apply To Work/Open File
PM20100             PM Apply To Open Temporary File
PM30300             PM Apply To History File

Sales Order Processing Batch
SOP10100            Sales Transaction Header Work/Open
SOP30200            Sales Transaction Header History

Sales Order Processing Batch Line Detail
SOP10200            Sales Transaction Line Detail Work/Open
SOP30300            Sales Transaction Line Detail History

Receivables Management Transactions
RM20101             RM Work/Open Transactions
RM30101             RM History Transactions

Receivables Management Distributions
RM10101             RM Distribution Work/Open
RM30301             RM Distribution History

Receivables Management Receipts
RM10201             RM Cash Receipts Work File

Receivables Management Apply Document
RM20201             RM Apply Work/Open Transactions
RM30201             RM Apply History Transactions

Payroll Transactions
UPR10302            Payroll Transactions
UPR30300            Payroll Transaction History
UPR30301            Payroll Transaction History Header
UPR30400            Payroll Distribution History Header
UPR30401            Payroll Distribution History Detail

ACA Employee Tables
UPR00905            Employee Master Work
UPR10109            Year-End Employee History

ACA Dependent Tables
UPR00904            Dependent Master
UPR10108            Year End Dependent History

Inventory Tables
IV30200                Inventory Transaction History
IV30300                Inventory Transaction Amounts History
IV30301                Inventory Transaction Detail History
SEE30303             Inventory Transaction History Detail

Company Tables
SY00500                Batch Activity

DYNAMICS Tables
ACTIVITY              User Activity
SY01500                Company Master