Finding out the value of your old accumulation of coins can be quite painful.
But dont panic!! There's plenty of help around if you know where to look.
Greg McDonlad publishes an annual "Pocket Guide to Australian Coins and Banknotes". Currently, in 2006, he's up to the thirteenth edition. Its nearly 500 pages of info on Aussie coins and banknotes, from a-to-z, from the year dot (i.e. the proclamation coins), through the holey dollars, square penny trials, gold sovereigns, pounds, shilling and pence and through to the present day. It covers all commemorative and collectors' issues, and provides plenty of info on grading, dealers, and details about coins in extensive footnotes. Greg McDonald also provides personal numismatic advice and assistance to sunscribers - a very wise investment I reckon.
Renniks also produce a price guide, "Renniks Australian Coin & Banknote Values", and reached 21 Editions in 2004. It's a larger format book, also with photos, informative details, and of course values (that I've found to be slightly more conservative than in the McDonald;s Guide). It also covers Australian tokens. Renniks of course are Australia's leading supplier of quality numismatic accessories, so you know thay they know thier stuff.. Ay.
If you really want conservative pricing though, have a look throught he Australian section of Krause's World Coins. Its a massive book, with one volume covering all the countries in the world's coin issuance over the course of a century. "World Coins" contains a little geographical info about each country as well as the price (in $US) of the coins that each country has produced. There is a seperate volume (or two:) for banknotes as well. It's pretty huge.
So all these books are great as ready references when you're looking for an coin or banknote for your collection on eBay. Its important to bear in mind though that especially in this field, in the end its all about supply and demand, and the real value of any coin or note is really what the market gives it when the hammer falls, so to speak.
Grading is a major issue in valuing coins. I suppose the best way to learn it is under expert guidance, but if that isn't easily available, ANDA (Australian Numismatic Dealers Association) has expert experienced members all over the country. They've also produced an excellent booklet on grading Australian predecimal coins. You can contact ANDA via their website - http://www.anda.com.au/ for that..
The Australian Numismatic Society has branches and meetings all over the country, and you can contact them for details of meetings near you via their website: http://www.the-ans.com/.
The McDonalds and Renniks books mentioned above are often found in public libraries, and the ANDA booklet on grading can be purchased from them.
I used to worry a bit about issues around grading and valuation, but now my focus is on enjoying my chosen hobby. Learning more about it, including how to recognise an excellent coin or banknote is all part of the fun, and I simply hope it stays that way !