You can make the ç with the US-International Keyboard by typing an apostrophe and then a c or C right after it, if you are using Windows.
Windows US International Keyboard
But I am not sure on other systems or keyboard layouts. For some reason, Windows Vista will not allow me to switch over to the regular French keyboard layout without removing my English keyboard layouts from the keyboard language list. But the US-International Keyboard layout covers nearly everything, grave (à), acute (é), umlauts (ö), tidle (ñ), carets (â) and cedilla (ç), plus a few others (ß, ¿, ø, æ). For some stupid reason, it does not have œ and so if I ever need that, I usually cut and paste it from another document.