I love spending other people's money, so I will second the nomination for a miter trimmer. I believe Rockler and Woodcraft also carry them.
Sure, it's about $100 (I can't remember exactly), but it does an excellent job.
Mine has 3 stops (45 on each side, and 90 degrees).
It also comes in handy because now you can use a bandsaw to crosscut and then use the trimmer to bring to a true 90.
I will also add that a miter trimmer is great for long pieces of trim, which might be a little difficult to handle on a tablesaw sled. If you are putting trim around doorways/windows, it will basically "pay for itself"
I use it a lot more than I thought I would.. If you can swing the cost, I highly recommend it. Also, keep an eye out for used ones. They pop up from time to time.