I need to sail from Mallorca to Port Napoleon (west of Marseille) in The Rhone esturary. Any recommendations of internet forecasts covering this area of the Med??
The French VHF forecasts can be received in Mallorca and are pretty accurate, especially at forecasting and announcing mistrals, which is your big potential problem on this passage.
I agree that MeteoFrance is good. If you subscribe to their Navimail service, only 4 Euros per month for 4 day forecasts, you can receive one of the few Med wave predictions in grib files. Two years ago I was most impressed when I saw this prior to a passage very similar to yours. It saved me a most uncomfortable 24 hours into 3 metre swells.
I now use XCweather a lot, the site is very user friendly, accurate and light on megabytes for GPRS use.
and the 3x daily broadcasts on Marine VHF Ch79 (preceeded by an announcement on Ch16) with hourly updates if Mistral is suspected, were also very accurate.
All the marinas post Meteo France reports in the Capitanerie if you are staging the journey.
We did Port Camargue > Cap D'Agde (1/2 day)
Cap D'Agde > Banyuls sur Mer (10 hours)
Banyuls > Palamos (10 hours)
Palamos > Barcelona (7 hours)
You could do the reverse except to head direct to Port Napoleon from Cap D'Agde on the final day and make a long day of it.