The Union 34 Stripe Rucksack with seatpost mount option looks like a really good idea on paper: pop it on your bike for going to the station (for example), park bike, pop rucksack on your back, away you go.
The alternatives are a normal backpack and getting off your bike with a sweaty back, or lugging a pannier when you're off the bike. Combining the best of both worlds could be a winner, but the Stripe doesn't quite deliver.
I had to have a spare set of retinas on standby looking at this Crumpler Dinky Di messenger bag, the colours are so loud they almost burst my eye balls.
The SKS Energy Bag is nicely made and easy to access, and it's pretty cheap too. Triathletes have been using top-bar-mounted energy hoppers for years, and they're becoming more popular among road riders too as they give you a handy place to chuck a few gels or your phone.
A leather saddlebag is a classic cycling accessory that my grandad would have found familiar. That said, it's hard to avoid the phrase 'Gucci manbag' when trying to describe this offering from Spa Cycles.
I have a Vaude backpack / Hydration pack for sale. It is brand new with tags and original packaging. This was an unwanted gift. The RRP is £59.99 (as printed on tag). I am selling the bag for £40 and can post within the UK for £2.
Multi-award winning Hyper 17 litre Vaude 2012 backpack for anything from an after-work-spin to an epic day tour.