As I was shooting down near Lake Burley Griffin (specifically in the International Flag Display on the southern shore of the lake) I was surprised to see this balloon almost on top of me. I later discovered that it was so close because it had been launched from a nearby park. Although I'd packed away most of my kit by then, I grabbed the 40D and took a bunch of (hand-held) shots of it as it went up... of which I'd judge this to be the most photogenic. It also restores my faith in the 24-105's IS capabilities.
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Edit 10 August 2024: I'm really surprised that I didn't do a lookup of the balloon back in the day, since it was a lot closer to my aviation nerd (and indeed piloting) days than it is now, 16 years later. And if you've seen any of my aviation galleries from the last few years, I typically go into chapter and verse about the aircraft.

So here we go. You can make out the registration on the balloon; VH-HIC. This is a Thunder & Colt Model 69A balloon. At this point I have some conflicting information. A couple of different reference sources say that VH-HIC was manufactured in the UK in 1996. Yet other sources say that the UK company Thunder & Colt (formed from a merger of two companies dating back to the 1970s) went into receivership and ceased operations in 1994. (A successor company, Lindstrand Balloons, was launched by the then managing director of Thunder & Colt but seems to have been a separate operation.) Of course it's possible that this balloon was manufactured before the company failed and just wasn't sold for a while; its first registered date was 20 Feb 1996.

In any case, it's still registered with the Civil Aviation Safety Authority at the time of writing, though the current registration holder (since 1 May 2024) has a Queensland rather than an ACT address so it may have moved north.