VBA array sort function?

Take a look here:
Edit: The referenced source (allexperts.com) has since closed, but here are the relevant author comments:

There are many algorithms available on the web for sorting. The most versatile and usually the quickest is the Quicksort algorithm. Below is a function for it.

Call it simply by passing an array of values (string or numeric; it doesn't matter) with the Lower Array Boundary (usually 0) and the Upper Array Boundary (i.e. UBound(myArray).)

Example: Call QuickSort(myArray, 0, UBound(myArray))

When it's done, myArray will be sorted and you can do what you want with it.
_{(Source: archive.org)}

Public Sub QuickSort(vArray As Variant, inLow As Long, inHi As Long)
  Dim pivot   As Variant
  Dim tmpSwap As Variant
  Dim tmpLow  As Long
  Dim tmpHi   As Long

  tmpLow = inLow
  tmpHi = inHi

  pivot = vArray((inLow + inHi) \ 2)

  While (tmpLow <= tmpHi)
     While (vArray(tmpLow) < pivot And tmpLow < inHi)
        tmpLow = tmpLow + 1
     Wend

     While (pivot < vArray(tmpHi) And tmpHi > inLow)
        tmpHi = tmpHi - 1
     Wend

     If (tmpLow <= tmpHi) Then
        tmpSwap = vArray(tmpLow)
        vArray(tmpLow) = vArray(tmpHi)
        vArray(tmpHi) = tmpSwap
        tmpLow = tmpLow + 1
        tmpHi = tmpHi - 1
     End If
  Wend

  If (inLow < tmpHi) Then QuickSort vArray, inLow, tmpHi
  If (tmpLow < inHi) Then QuickSort vArray, tmpLow, inHi
End Sub

Note that this only works with single-dimensional (aka "normal"?) arrays. (There's a working multi-dimensional array QuickSort here.)

Explanation in German but the code is a well-tested in-place implementation:

Private Sub QuickSort(ByRef Field() As String, ByVal LB As Long, ByVal UB As Long)
    Dim P1 As Long, P2 As Long, Ref As String, TEMP As String

    P1 = LB
    P2 = UB
    Ref = Field((P1 + P2) / 2)

    Do
        Do While (Field(P1) < Ref)
            P1 = P1 + 1
        Loop

        Do While (Field(P2) > Ref)
            P2 = P2 - 1
        Loop

        If P1 <= P2 Then
            TEMP = Field(P1)
            Field(P1) = Field(P2)
            Field(P2) = TEMP

            P1 = P1 + 1
            P2 = P2 - 1
        End If
    Loop Until (P1 > P2)

    If LB < P2 Then Call QuickSort(Field, LB, P2)
    If P1 < UB Then Call QuickSort(Field, P1, UB)
End Sub

Invoked like this:

Call QuickSort(MyArray, LBound(MyArray), UBound(MyArray))

Heapsort implementation. An O(n log(n)) (both average and worst case), in place, unstable sorting algorithm.

Use with: Call HeapSort(A), where A is a one dimensional array of variants, with Option Base 1.

Sub SiftUp(A() As Variant, I As Long)
    Dim K As Long, P As Long, S As Variant
    K = I
    While K > 1
        P = K \ 2
        If A(K) > A(P) Then
            S = A(P): A(P) = A(K): A(K) = S
            K = P
        Else
            Exit Sub
        End If
    Wend
End Sub

Sub SiftDown(A() As Variant, I As Long)
    Dim K As Long, L As Long, S As Variant
    K = 1
    Do
        L = K + K
        If L > I Then Exit Sub
        If L + 1 <= I Then
            If A(L + 1) > A(L) Then L = L + 1
        End If
        If A(K) < A(L) Then
            S = A(K): A(K) = A(L): A(L) = S
            K = L
        Else
            Exit Sub
        End If
    Loop
End Sub

Sub HeapSort(A() As Variant)
    Dim N As Long, I As Long, S As Variant
    N = UBound(A)
    For I = 2 To N
        Call SiftUp(A, I)
    Next I
    For I = N To 2 Step -1
        S = A(I): A(I) = A(1): A(1) = S
        Call SiftDown(A, I - 1)
    Next
End Sub

@Prasand Kumar, here's a complete sort routine based on Prasand's concepts:

Public Sub ArrayListSort(ByRef SortArray As Variant)
    '
    'Uses the sort capabilities of a System.Collections.ArrayList object to sort an array of values of any simple
    'data-type.
    '
    'AUTHOR: Peter Straton
    '
    'CREDIT: Derived from Prasand Kumar's post at: https://stackoverflow.com/questions/152319/vba-array-sort-function
    '
    '*************************************************************************************************************

    Static ArrayListObj As Object
    Dim i As Long
    Dim LBnd As Long
    Dim UBnd As Long

    LBnd = LBound(SortArray)
    UBnd = UBound(SortArray)

    'If necessary, create the ArrayList object, to be used to sort the specified array's values

    If ArrayListObj Is Nothing Then
        Set ArrayListObj = CreateObject("System.Collections.ArrayList")
    Else
        ArrayListObj.Clear  'Already allocated so just clear any old contents
    End If

    'Add the ArrayList elements from the array of values to be sorted. (There appears to be no way to do this
    'using a single assignment statement.)

    For i = LBnd To UBnd
        ArrayListObj.Add SortArray(i)
    Next i

    ArrayListObj.Sort   'Do the sort

    'Transfer the sorted ArrayList values back to the original array, which can be done with a single assignment
    'statement.  But the result is always zero-based so then, if necessary, adjust the resulting array to match
    'its original index base.

    SortArray = ArrayListObj.ToArray
    If LBnd <> 0 Then ReDim Preserve SortArray(LBnd To UBnd)
End Sub

Somewhat related, but I was also looking for a native excel VBA solution since advanced data structures (Dictionaries, etc.) aren't working in my environment. The following implements sorting via a binary tree in VBA:

• Assumes array is populated one by one
• Removes duplicates
• Returns a separated string ("0|2|3|4|9") which can then be split.

I used it for returning a raw sorted enumeration of rows selected for an arbitrarily selected range

Private Enum LeafType: tEMPTY: tTree: tValue: End Enum
Private Left As Variant, Right As Variant, Center As Variant
Private LeftType As LeafType, RightType As LeafType, CenterType As LeafType
Public Sub Add(x As Variant)
    If CenterType = tEMPTY Then
        Center = x
        CenterType = tValue
    ElseIf x > Center Then
        If RightType = tEMPTY Then
            Right = x
            RightType = tValue
        ElseIf RightType = tTree Then
            Right.Add x
        ElseIf x <> Right Then
            curLeaf = Right
            Set Right = New TreeList
            Right.Add curLeaf
            Right.Add x
            RightType = tTree
        End If
    ElseIf x < Center Then
        If LeftType = tEMPTY Then
            Left = x
            LeftType = tValue
        ElseIf LeftType = tTree Then
            Left.Add x
        ElseIf x <> Left Then
            curLeaf = Left
            Set Left = New TreeList
            Left.Add curLeaf
            Left.Add x
            LeftType = tTree
        End If
    End If
End Sub
Public Function GetList$()
    Const sep$ = "|"
    If LeftType = tValue Then
        LeftList$ = Left & sep
    ElseIf LeftType = tTree Then
        LeftList = Left.GetList & sep
    End If
    If RightType = tValue Then
        RightList$ = sep & Right
    ElseIf RightType = tTree Then
        RightList = sep & Right.GetList
    End If
    GetList = LeftList & Center & RightList
End Function

'Sample code
Dim Tree As new TreeList
Tree.Add("0")
Tree.Add("2")
Tree.Add("2")
Tree.Add("-1")
Debug.Print Tree.GetList() 'prints "-1|0|2"
sortedList = Split(Tree.GetList(),"|")