I have a friend who makes pixelart for my games, so luckily gfx part of this problem is mostly non-existent. I know how to do some basic stuff, be it GIMP or a more pixelart-focused editor - so if I'm missing something, I can create some acceptably-looking placedholder. Or, I can always try asking another one of my friends.

For sounds, I sometimes use findsounds.com, but most of the time - my quite extensive .wav library taken from a lot of games, game mods et cetera, quite often edited using Audacity.

Music is the biggest bummer, as none of my friends really does anything in this field.