Yep, both Bottas and Massa were announced today for a nice collect at $1.13 for the former.

Current WCC odds are:
$1.67 Mercedes
$2.50 Red Bull
$10.00 Ferrari

I wouldn't bother with any other team just yet below the top 3. I think Red Bull are still good value, given Merc has lost Rosberg and Paddy Lowe.

Ferrari are making a HUGE push after their disastrous 2016. If they don't deliver at least a race win, heads will roll in Maranello.

Cars are being launched from 21st February for the first test a week later.

Australian Grand Prix
current market

Lewis Hamilton $1.90
Max Verstappen $4.50
Valtteri Bottas $4.50
Daniel Ricciardo $5
Sebastian Vettel $15
Others $26 or better

Lewis Hamilton, too short for me.
Australia has always thrown up surprises being Round 1 and last year was only because of the crash on lap 18 which allowed Nico to win and Lewis to run second.
This year apparently there has been some major specification change yet again.
So $1.90 is definitely unders for me.

Not sure, but aren't there some more engine mods as well?

They're expecting lap times to be cut by around 3 seconds - increased aero & mechanical grip, combined with revised tyres to suit slightly heavier cars. Faster corner speeds rather than top speeds.

Market has changed considerably

Lewis Hamilton $2.48
Sebastian Vettel $4.60
Valtteri Bottas $7.60
Kimi Raikkonen $9.80
Daniel Ricciardo $12
Max Verstappen $13.50

Others $100 or better

Unfortunately I was not able to get onto the forum in the last month or so.

Ferrari showed blistering pace in testing and to no surprised were a match for Mercedes in Melbourne.

Prior to the first race, I was able to get Vettel @ $22 for the WDC and Kimi @ $55. After quali, Vettel was paying $4.00 for the race win. Unfortunately Red Bull and a punt on McLaren pushed out the wrong way.

I think Bottas is a value bet given his outing in Melbourne which is one of his worst circuits. Vettel and Ferrari can definitely have a crack at both championships.

Chinese Grand Prix Winner

Lewis Hamilton $1.85
Sebastian Vettel $3.05
Valtteri Bottas $14.50
Kimi Raikkonen $21
Daniel Ricciardo $44
Max Verstappen $90

Others $300 or better

dominant display by Hamilton

Ferrari's Formula One championship leader Sebastian Vettel will face no further sanction for his 'road rage' collision with Lewis Hamilton at the Azerbaijan Grand Prix.
The German, a four times world champion, was given a 10 second stop-and-go penalty during the race for angrily banging wheels with his Mercedes rival while they were behind the safety car.
The International Autmobile Federation said Vettel, who turned 30 on Monday, attended a meeting at its Paris headquarters.
He admitted full responsibility, apologised and also "committed to devote personal time over the next 12 months to educational activities across a variety of FIA championships and events."
The governing body said that "in light of these developments, FIA President Jean Todt decided that on this occasion the matter should be closed."
-Source AAP.

A 10 second penalty is fine for taking another drivers racing line and causing a collision, but a road rage incident behind a safety car is inexcusable as Hamilton pointed out over his radio in a pointed but subtle fashion. These things have a way of evening themselves out, and I can see Hamilton beating Vettel due to better luck as well as skill in Austria.