Cindi, make sure you outline or somehow make sure that they can't write in the seam line! I did not do this for my daughters wedding, and I am going to loose some writing to the seam allowance!

I use "Tulip" fabric markers for my labels. You press them after writing and then allow to sit for 24 hours. They are fine point, don't bleed, easy to use and last forever. Also they are not as expensive as Pigma, that is not to say that Pigma isn't a quality product because it is.

I got the Sharpie colored pens and it says right on the package "not for fabric" so I recommend reading the label.
My favorite is the pigma pen.

I have several quilts that I have made with signatures these quilts are well loved and have been washed many times. The sharpies will totally disappear over time the pygma pens are still as nice as the day they were signed I plan on getting some of the Crayola brand fabric markers.

Another vote for the pigma pens for me.

I have always used Pigma pens for my labels. However, if the quilt gets washed a lot the ink does fade - eventually until it is illegible. I made my dad a quilt that he used at the nursing home and after 4 years of frequent washings, the label was so faint that I could barely read it. I re-wrote over it.

I iron my fabric to freezer paper to make it stiff before I write on it. Thanks for all the suggestions.

Micron Pens are great for labels. You can find them at some LQS or Joann's and Michael's. They come in assorted colors and point sizes.

The test at Freckled Whimsey said something I couldn't believe until I checked it myself. The Pigma Micron company website says that the pens are NOT to be washed! Here's the quote - Fabric design* note - the inks on fabrics are for "decorative purposes only" - meaning do not launder.

Here's the link, it's near the bottom of the page. http://sakuraofamerica.com/pen-archival

Tate

Any more updates on this, about the pens? My daughter just called and asked if I would help her make siggy blocks for her wedding in August.