I've made this t-shirt as a present for my wife Miranda, a professional editor and writer.
A few tips.
Type your text, choose colour. Here I chose pure black for the word Editor: use CMYK sliders in the colour well to set CM and Y to nil and K (black) to 100 percent. The grey for 'the' I copied from the French Paper web-site: click on the magnifying glass (colour picker) in the colour well and then click on the colour you want to copy.
It may be that text looks too thin – the letters are too spaced. Tighten them up: highlight the text and in Text Inspector reduce Spacing. Don't overdo, otherwise the text will be difficult to read.
Turn text into image. Print to PDF, save to iPhoto to make a JPEG file instantly or make a screenshot (Command+Shift+4 and drag crosshairs over the text) to get a PNG file. For best results use the PDF format and then re-save it as JPEG for uploading to a t-shirt making web-site.
Now, the image you get will probably have a white background. To put it on a t-shirt you need to remove it. Import the image back into Pages and remove the white background with Instant Alpha. Copy and paste it into the t-shirt printing application. If that doesn't work, create another shape in your Pages document, in Graphic Inspector choose None for colour fill and None for Stroke and move that transparent shape over the image of the text. Select both, copy and paste into an image making application, Preview for example. The transparent background should be preserved.
The credit for this trick goes to Ken Drake of KeynoteUser.com and is also described by Macworld. I've tested it and it works.
I've used CafePress, but there are other print-on-demand resources there, just google to see what suits you best. I placed the order on their web-site, paid through PayPal, the order was processed and confirmed within 24 hours, shipped within 48 hours and arrived in 10 days. The quality of the print and the shirt itself is very good.