Acacia elongata is a small, open plant of upright habit.  Around here (western Sydney) it never seems to grow to more than about 1.5 - 2 metres high but it can reach 4 metres in other areas.  It grows right along eastern New South Wales and extends into north-eastern Victoria.  It's sometimes called 'Swamp Wattle' but I'm not convinced that's an appropriate name.

The floral emblem of Australia is, of course, the Golden Wattle (Acacia pycnantha).  The National Botanic Gardens has an excellent page on this species here and, the place to find out about acacias generally is World Wide Wattle.

Of course, if you really want to get into the spirit of Wattle Day you could adopt the recommendation of the Wattle Day Association that all Australians:

• WEAR the green and the gold (Australia’s colours) or a sprig of wattle
• WELCOME each other with a G’day, a smile, a wink or a handshake in the same way as the wattle blossoms gold to welcome in the Australian Spring.

But, then again.......