There are loads of good places. Here are some of our favourites:
Ryde - has a marina but dries. Timboli will be able to tell you when it's accessible.
Cowes - Town Quay but can get very busy in summer.
River Medina - Folly Inn has its own pontoon but again, busy in summer.
Yarmouth - tie up at along Town Wall. Really friendly berthing master.
Ventnor - you'll probably get a ride to shore from the Harbourmaster (Dan) or the local fisherman's son in his SIB (he's about 10 years old!!). The tying-up pontoon is a bit rickety and you need to follow the channel markers in very carefully. I'd advise you to go by car at low tide and have a good luck at the entrance and the harbour as it's quite a new harbour and doesn't appear on some charts. It's also of variable depth.