Singly-linked list object pool with the list members embedded in the contained object.

ObjectWithPool.cs

public sealed class MyObject : IDisposable
{
    /// <summary>
    /// Used by the pool.
    /// </summary>
    private MyObject _next;

    // TODO: Add other members here.

    public static MyObject Create()
    {
        var result = Pool.Instance.TryGet();
        if (result != null)
            return result;
        return new MyObject();
    }

    public void Dispose()
    {
        Pool.Instance.Put(this);
    }

    private sealed class Pool
    {
        private readonly object _mutex = new object();
        private MyObject _first;

        public MyObject TryGet()
        {
            lock (_mutex)
            {
                var result = _first;
                if (result == null)
                    return result;
                _first = _first._next;
                return result;
            }
        }

        public void Put(MyObject element)
        {
            lock (_mutex)
            {
                element._next = _first;
                _first = element;
            }
        }

        public static readonly Pool Instance = new Pool();
    }
}