Before I had the silhouette I found various ways to make my own letters and numbers to stick on blocks like this Christmas count down set. The best thing I found was to use contact paper (French: film de protection adhésif) which is self adhesive and comes in a bunch of different colors and you can usually find quite cheap ones too (in France I get them at VIMA where they cost less than 4 euros!).This is what contact paper looks like, it always comes in a roll and what I like about this technique is that you waste very litlle of the stuff on your projects so a roll can last a very long time:) (the contact paper in the picture is clear by the way)
So to start just open a word document and choose the font, font size and words you want to have on your project and print them out on normal thin printer paper (the thinner it is, the easier it will be to cut it precisely)
For the inside of the letters such as the B and the e I used my craft knife to gently cut those out.
Then take your contact paper (I used black), shiny side down and trace your letters on to the back of the contact paper (the side that is actually made of paper!), be sure to invert the letters so if you printed your text out in black make sure the black side is facing down....otherwise you'll have to trace it again...I learned the hard way.Then use your scissors to cut the letters out again and for the inside use your craft knife again. Once you get the hang of it the craft knife is quite easy to use, I find that rotating the paper instead of the the knife works best. Then you just need to remove the backing and stick it onto your project!