See the question and my original answer on StackOverflow

Here is a console app utility (in C#) that dumps the list of toolset (for each available configuration). You need to add a reference to Microsoft.Build to be able to compile. Note the proper list of toolset is supposed to depend on the project to build:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace ListToolsets
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length == 0)
            {
                Console.WriteLine("Format is ListToolsets <project file path>");
                return;
            }

            foreach (var toolset in PlatformToolset.GetPlatformToolsets(args[0]))
            {
                Console.WriteLine(toolset.Platform);
                foreach (string ts in toolset.Toolsets)
                {
                    Console.WriteLine(" " + ts);
                }
            }
        }

    }

    public class PlatformToolset
    {
        private PlatformToolset()
        {
            Toolsets = new List<string>();
        }

        public string Platform { get; private set; }
        public IList<string> Toolsets { get; private set; }

        public static IList<PlatformToolset> GetPlatformToolsets(string projectPath)
        {
            var list = new List<PlatformToolset>();
            var project = new Microsoft.Build.Evaluation.Project(projectPath);
            AddPlatformToolsets(project, @"$(VCTargetsPath14)\Platforms", list);
            AddPlatformToolsets(project, @"$(VCTargetsPath12)\Platforms", list);
            AddPlatformToolsets(project, @"$(VCTargetsPath11)\Platforms", list);
            AddPlatformToolsets(project, @"$(VCTargetsPath10)\Platforms", list);
            return list;
        }

        private static void AddPlatformToolsets(Microsoft.Build.Evaluation.Project project, string path, IList<PlatformToolset> list)
        {
            string platforms = Path.GetFullPath(project.ExpandString(path));
            if (!Directory.Exists(platforms))
                return;

            foreach (string platformPath in Directory.GetDirectories(platforms))
            {
                string platform = Path.GetFileName(platformPath);
                PlatformToolset ts = list.FirstOrDefault(t => t.Platform == platform);
                if (ts == null)
                {
                    ts = new PlatformToolset();
                    ts.Platform = platform;
                    list.Add(ts);
                }

                foreach (string toolset in Directory.GetDirectories(Path.Combine(platformPath, "PlatformToolsets")))
                {
                    string name = Path.GetFileName(toolset);
                    string friendlyName = project.GetPropertyValue("_PlatformToolsetFriendlyNameFor_" + name);
                    ts.Toolsets.Add(string.IsNullOrWhiteSpace(friendlyName) ? name : friendlyName);
                }
            }
        }
    }
}