best day to visit Versailles?

Any day but Tuesday, when most of the museums in Paris are closed. If you're going during the summer, they have fountain shows on the weekends, it will be busier but if you want to see the show, that's when to go.

I would pick the day with the best weather, particularly for the first trip. On my last visit, I went out there pretty much the first full day after I arrived, when weather was clear. This was my second visit there, and I knew I wanted to see the gardens and go to the Petit Trianon, Marie Antionette's little farm, etc. which are wonderful (just view the new Marie Antionette movie to get a peek at these places). Good weather is really an important consideration in my opinion. I have only been on weekdays, and it has not been real crowded. Next time I go though, I will probably go on the weekend to see the fountains -- Judging by what I have seen of them turned off -- I imagine they will be magnificent.

the palace is under restoration at the moment. if it's your first time, you'll still have a lot of "wow"s, but otherwise you keep expectation low!

This will be my first time to France. Is it still worthwhile to go to Versailles? I plan on also spending a few days in Bayeux. Any other day trips from Paris I should make besides Versailles?

if first time still go see the garden and the palace, but plan on coming back to paris later in the afternoon for another site to make your money worth (if you buy a museum pass, 2/4/6 days).

loire valley or normandy are popular day trips. if you can get a car would be the best. see a couple of castles in loire valley, or go to caen for the war museum (not bad), bayuex for the church and tapastry, and then drive around d-day beaches. there are a lot of museums in that area, so you may skip caen's (expensive) and see a few by the beach or in bayeux.