Here are a few, and there are probably quite a few more where these came from:
Bolas have been used effectively against a wide variety of animals. http://en.wikipedia.org/wiki/Bolas
It might be a little awkward to use a traditional bola while riding a bike (though it could be done). An 'autobola' could be designed along the lines of a spearfishing ***. The balls could be propelled with surgical tubing.
A very bright flash could temporarily blind a dog:
The Inflatable Bear:
A large, snarling, suddenly inflating bear looming over the dog may be effective.
Recorded sounds that have the desired effects on dogs. Rattlesnake. Shotgun action. Angry, scolding owner. Animal sounds that trigger instinctive responses.
Variation: practice with voice to make the most effective sounds.
Deployable and Irresistible Stuffed Animals:
Dangling from stiff wire alongside the bike -- perhaps two or three feet out.
They could be laced with superhot cayenne pepper.
There may be ways of designing systems that would entangle the feet of a pursuing dog(s).
Lightweight netting (like the bird netting sold to gardeners and farmers), combined with some kind of very sticky substance (like that used in glue traps).
Volume-adjustable Piezo Emitters:
Used in alarm systems, and for other applications, these can be very loud, and they can produce some extremely unusual sounds that give dogs pause.
Rubber Bullets and Beanbag Stunguns:
Used by law enforcement and riot control. http://en.wikipedia.org/wiki/Riot_***
Sticky Attack Dolls:
I've experienced a few of these myself. The sky's the limit on these designs.
There were some others too. I'll try to remember them.
Any additional ideas would be welcome here.