System.Collections

System.Collections.ArrayList	This can work with any type of data (objects, strutcs or primitive types) Doesn't have a (key,value) relationship
System.Collections.BitArray
System.Collections.Hashtable
System.Collections.Queue	First in, first out collection
System.Collections.SortedList
System.Collections.Stack	Last in, first out collection

System.Collections.ArrayList

Added in .NET 1.1
more details

System.Collections.BitArray

Added in .NET 1.1

System.Collections.BitArray

System.Collections.Queue

Added in .NET 1.1

System.Collections.Queue

The generic version of this collection is System.Collections.Generic.Queue

System.Collections.SortedList

Added in .NET 1.1

System.Collections.SortedList

Methods

Add	Appends an element after the last element in the collection and returns the index where it was inserted.
Clear	Removes all elements from the collection.
Clone
Contains	Returns TRUE if an element exists in the collection.
ContainsKey
ContainsValue
CopyTo	Copies the elements from the collection to a new one-dimensional array, starting at the specified index in the array.
GetByIndex	Gets the value at a specified index
GetEnumerator	Returns an enumerator to iterate an ArrayList
GetKey
GetKeyList
GetValueList
IndexOfKey
IndexOfValue
Remove	Removes an element from the collection
RemoveAt	Removes an element at the specified index from the collection
SetByIndex
Synchronized	Alphabetically sorts the elements
TrimToSize

Properties

Capacity	Property contains the number of elements the srray can currently hold.
Count	Returns the number of elements in the collection.
IsFixedSize	Returns TRUE if no more elements can be added to the collection.
IsReadOnly	Returns TRUE is the elements cannot be altered.
IsSynchronized
Item
Keys
SyncRoot
Values

The generic version of this collection is System.Collections.Generic.SortedList

System.Collections.Stack

Added in .NET 1.1

System.Collections.Stack

The generic version of this collection is System.Collections.Generic.Stack

System.Collections.ICollection

Added in .NET 1.1
This interface extended the IEnumerable interface.
This is the medium functionality and gives you foreach and a count
The ICollection interface is the base interface for classes in the System.Collections namespace.