I will be in between jobs in late October/Early November and have a total of 3 weeks for a trip to Oz.

3 weeks seems a long time but probably isn't, I have to get to and from Austalia from the UK in that time also.

Any suggestions on good trips within Oz for that period?

I definitely want to see Sydney. I was thinking of travelling overland down as far as Melbourne/Adelaide. Is that worth the trip or is it better to go North?

I also was planning on flying to Perth for 5 or 6 days, I have friends there.

So my flights would probably involve me flying into Perth, and out of Sydney, or vice versa.

Any suggested itineraries would be appreciated?

Couchcarrot

I went to Australia & NZ for the month of Jan. 2001. You need to calculate 2
days lost in travel time from the 3 weeks. You'll gain a day going & lose it returning.

If you travel north, around Cairns, where my trip started, be sure to go to
the Great Barrier Reef. This was the high point of it. There you can snorkel or
take a tour under the sea in a glass bottom boat. Ride on the "Silver Bullet,
enjoy the huge buffet set up there on a pontoon. While in Sydney, climb the
Harbor Bridge. This doesn't cost much. You'll be hooked up to other climbers
and be able to see Sydney and the harbor from a great vantage point.
I've never been to Western Australia (Perth), but if you can get to Melbourne,
I think it will be worth you time. It's majestic. If you can fit in 2 or 3 days
to see the North and South Islands of New Zealand, you should do it. It's
only about a 3-hour flight from Sydney, Aus., and I liked it even more.
There are casinos galore in Auckland, water sports in Queenstown, NZ
(not Queensland, that's where Melbourne is), and Christchurch will likely
remind you of London, or other cities in England. I was in England in 1991.

One last reminder, before you leave the Southern Hemisphere, don't forget
to look up at the sky at night and if possible maybe take a picture of the
"Southern Cross." which, as you know, won't be visible in the sky once you
return north of the Equator.

hanginaround

couchcarrot,
melbourne is in the state of victoria, not queensland, brisbane is in q.l.d
back to the main question: if you want to see the "real outback" then your best bet is to get to adelaide, south australia, and get on the train to perth- going across the nullabour. or go on the "ghan" train from adelaide to alice springs. if you want the hot tropics stick to queensland, sunshine coast is well worth a visit. if you want the hussle and bussle go to sydney, and/or melbourne. if you want cold and snow head to tassmania, or victoria/n.s.w borders

TechAngel

Sydney would be great for 3-4 days. There's a lot to see and do, day and night. A ferry to Manly Beach would be a good half-day trip. I recommend a few days in Cairns, Queensland, if you like snorkelling or diving and would like to get out to the Great Barrier Reef. There's rainforest and sugar cane up there too if you're into nature. For your general itinerary, flying from Europe you could route via Singapore (eg with Qantas) and fly in to Sydney, then up to Cairns, then across to Perth, and then back out to Singapore and Europe. While in Perth you could drive south (3 hrs) to Margaret River where there are great wineries and great surfing. Rottnest Island, a short ferry ride from Fremantle (near Perth), would be a good day-trip in the summer. Fremantle's good too for pubs and restaurants, particularly fresh seafood.