The following list has lots of free (and not so free) resources for building inclusive communication to print-out. To start off though, you'll need some software to edit photos with. If you don't have anything like Photoshop, I recommend looking at some of the really good free on-line picture editing systems such as Pixlr.com and the screen grab utility PixTick.
You can find photos galore from the likes of Google Images and Flickr. For symbols and systems to boost inclusive communication, have a good root round the following:
ARASAAC - Searchable symbols from a hugely impressive range.
Sclera - great for sight impaired too if made at the appropriate size. Worth checking out their links page too.
How It Is - lots of symbols based around feelings - "An image vocabulary for children about feelings, rights and safety, personal care and sexuality".
Personal Communication Passports - Great for many children and adults alike to get across things that are important to them.
Possyan-La-Coocan: Symbols from Japan.
SEN Teacher - Some lovely resources, such as clocks, money and games that you can tailor-adjust yourself.
Noun Project - A variety of free icons and symbols (not compatible with Internet Explorer, so use something like Firefox of Chrome if you can).
Teaching Learners With Multiple Special Needs - All this fine blog's symbol related posts. I recommend researching Kate's "Symbol and Photo Sets and Programs to Use Them" post for a huge range of resources.
Partners in Rhyme - Free sounds. Could be very useful tying up with cheap sound devices such as Talking Tins and Talking photo albums.
SymbolWorld - A fine news and features magazine composed in symbols.
iSpeek - Free communication passports and more.
Symbaloo - Superb symbol based front end to the internet.
Through the Maze Symbols - Pretty essential range, neatly organised. UPDATE: Presently unavailable (April 2011)