Yeah, as Crash said, Visual Studio is the premiere tool. Visual Studio 2010 is awesome, probably the best version of Visual Studio ever released.
Stick with C#, if you've worked with Java and C. It's a K&R language, so it should feel familiar syntactically (though paradigms are a bit different).
VB.Net's not bad, but it's wordy and not as terse as C#. Learning 3.5 and 4.0 will benefit you greatly, and stick with .NET, it's going to be MS future platform for development (IMO).
A word about Redgate: if you can afford it, get it. I manage multiple environments (dev, test/staging, demo and production) and Redgate helps me manage my SQL backends like you wouldn't imagine. SQL Compare and SQL Data Generator have been uber-helpful, I cried when I began using it. SQL Compare helps me manage my schemas far more efficiently than scripts alone, and with multiple environments, you wouldn't want to keep juggling script after script.
For iOS development, yes, you'll need a Mac, but if you have web dev experience look into PhoneGap (www.phonegap.com
). I'm eval'ing it right now and I like it. It uses jQuery, XHTML and CSS inside XCode and it will compile it into an objective-c executable. One of my main lessons learnt was this: Objective-C is FUGLY. It's like a retarded chimp put it together (and I'm a Mac fanboy, btw).
A lot of the tools Crash listed really help (Notepad++ is the love of my life), and if you can dump the cash for these tools, by all means do so.