An A-Z Index of Windows VBScript commands:

A:

   Abs(number)     Absolute (positive) value of number
  .AppActivate     Activate running command
   Array(el1,el2,el3)   Add values to an Array variable
   Arguments       Command line arguments
   Asc(String)     Return ASCII code for string
   AscW(String)    Return Unicode code for string
  .BrowseForFolder Prompt the user to select a folder

C:

   Call subroutine (arguments) or  subroutine arguments
   CBool(expression)  Convert expression to Boolean (True/False) •
   CByte(expression)  Convert expression to Byte (0-255) •
   CCur(expression)   Convert expression to Currency (numeric) •
   CDate(expression)  Convert expression to Date •
   CDbl(expression)   Convert expression to Double (up to 1.79x10308) •
   Chr(ChrCode)       Return the string character for ChrCode (ASCII code)
   ChrB(ChrCode)      Return the string character for ChrCode (Byte code)
   ChrW(ChrCode)      Return the string character for ChrCode (Unicode/DBCS)
   CInt(expression)   Convert expression to Integer •
   CLng(expression)   Convert expression to long •
   CSng(expression)   Convert expression to single •
   CStr(expression)   Convert expression to a string •
  .CreateObject     Create an automation object / run an external command
  .CreateShortcut   Create Shortcut
   cscript          Run a VBScript .vbs file
  .CurrentDirectory Retrieve or change the current directory

D:

   Date()         The current system date
   DateAdd        Add a time interval to a Date
   DateDiff       Return the time interval between two dates
   DatePart       Return part of a given date
   DateSerial     Return a Date from a numeric Year, Month and Day
   DateValue      Return a Date from a string expression
   Day(date)      Return the day component of date (1-31)
   Dim            Declare a new variable or array variable
   Do..Loop       Repeat a block of statements
   Drives
   Drive Map     .MapNetworkDrive - .Enum - .Remove

E:

  .Echo           Echo text to screen, also StdOut.Write /.Popup
   End            End a procedure or code block
   Environment Variables  - Expand - .Delete/Remove
   Escape(String) Return only ASCII characters from a Unicode string.
   Eval(expr)     Evaluate an expression
  .Exec           Run a command
   Exp(n)         Return e (base of natural logs) raised to a power n.
   Exit           Exit a block of code immediately

F:

   FileSystemObject Work with Drives, Folders and Files
   Filter         Produce an array by filtering an existing array
   Fix(number)    Return the integer portion of a number
   For...Next     Repeat a block of statements a given number of times
   For Each...    Loop through the items in a collection or array
   FormatCurrency Format a number with a currency symbol
   FormatNumber   Format a number
   FormatPercent  Format a number with a % symbol
   FormatDateTime Format a Date/Time value
   Function       Define a function procedure

G:

   GetLocale()    Return the Regional LocaleID
  .GetObject      Get an Automation object

H:

   Hex(number)    Return the hex value of number
   Hour(time)     Return the hour component of time
I:
   If..Then       Conditionally execute a block of statements
   InputBox       Prompt for user input
   InStr          Find one string within another
   InStrRev       Find one string within another, starting from the end
   Int(number)    Return the integer portion of a number
   IsArray(varname)      Is varname an array?
   IsDate(expression)    Is expression a DateTime?
   IsEmpty(expression)   Is expression initialised?
   IsNull(expression)    Is expression NULL?
   IsNumeric(expression) Is expression a Numeric?
   IsObject(expression)  Is expression an object?
   Join           Combine the contents of an array into a single variable.

L:

   LBound             Return the smallest subscript for an array.
   LCase(String)      Return String in lower case
   Left(String,len)   Return the leftmost len characters of string
   LeftB(String,len)  Return the leftmost len bytes of string
   Len(String)    Return length of string in characters
   LenB(String)   Return length of string in Bytes
   Log(number)    Return natural log of number
  .LogEvent       Log an item in the Event log
   LTrim(String)  Remove any leading spaces from a string expression   

M:

  .MapNetworkDrive Drive Map     
   Mid            Return a mid-section from a string
   Minute(time)   Return the minute component of time
   Month(date)    Return the month component of date
   MonthName      Convert a month number to a descriptive Month
   MsgBox         Display a dialogue box message
   Now            Return the current Date and Time

O:

   On Error       Error handling
   Option Explicit   Force all variables to be defined

P:

  .AddPrinterConn / .AddWindowsPrConn Add Printer connection
  .EnumPrinterConnections   List Printer connections
  .SetDefaultPrinter        Set default printer
  .RemovePrinterConnection  Remove printer connection
   Private VarName          Declare a local variable/array variable
   Public VarName           Declare a public variable/array variable

Q:

  .Quit            Quit

R:

   Randomize(number)   Initialise the random number generator
  .ReadLine       Accept user text input
   ReDim          Resize a dynamic array
   RegExp         Regular expression search object
  .RegDelete      Registry, delete
  .RegRead        Registry, read
  .RegWrite       Registry, write
   REM            Add a Comment
   Replace        Find and replace text
   RGB(Red,Green,Blue) Return a system color code
   Right(String,len)   Return the rightmost len characters of string
   RightB(String,len)  Return the rightmost len bytes of string
   Rnd            Return a random number 
   Round          Round a number to n decimal places
   RTrim(String)  Remove any trailing spaces from a string expression
  .Run a command

S:

   Second(time)   Return the second component of time
   Select...Case  Conditionally execute a block of statements
  .SendKeys
   Set variable = object   Assign an object reference
   SetLocale(LocaleID)     Set the Regional LocaleID
   Sgn(number)             The sign of a number
  .ShellExecute   Run a script/application in the Windows Shell
   Shortcut create .CreateShortcut
  .Sleep
   Space          Return a string consisting of spaces.
  .SpecialFolders Path to Desktop,Start menu, Programs...
   Split          Parse a string of delimited values into an array
   Sqr(number)    Square root
   StrComp        Compare two strings
   String         Create a string with a single character repeated
   StrReverse     Reverse a string
   Sub            Declare a sub procedure

T:

   Time()         The current system time
   Timer()        The number of seconds since midnight
   TimeSerial     Construct a Time value from Hours, Minutes and seconds
   TimeValue      Convert a string to a Time value
   Trim(String)   Remove leading and trailing spaces from string
   TypeName       Return variable type (variant subtype).

U:

   UBound         Return the largest subscript for an array dimension
   UCase(String)  Uppercase String
   UnEscape(Str)  Return Unicode characters from an escaped ASCII string

W:

   Weekday        Return the day of the week (1-7)
   WeekdayName    Return the named day of the week
   While...Wend   Conditionally repeat a block of statements
   With           Assign multiple properties of an object
   Year(date)     Return the year component of date (1-12)
   ' Remark       Add a Comment