If you are planning to use Visual Studio .NET, you should install also Nokia Developer's Suite. It provides a number of wizards and automated functions that provide Symbian OS support in Visual Studio .NET 2003 with the minimum of manual configuration.
A recent addition is Carbide.c++. It provides a free IDE, based on Eclipse. The free version includes debugging on emulator (that's all you get on Visual Studio as well), commercial versions enable on-device debugging (on selected phone models).
For 7610, with the camera plug-in, and Visual Studio, get 2nd Ed, FP 1, MS & Borland (FP = Feature Pack). That's really the SDK 2.1. Install the SDK. Then, under "Other C++ tools for specific devices/platforms", get Nokia 7610 Camera Plug-in for Series 60 SDK 2.1 for Symbian OS and install that too. To repeat, you need to install basic SDK first and only then the 7610 / camera SDK on top of that. This version of SDK works on both MS .NET (VC++7.0) and MSVC++6.0 IDEs, as well as the Borland tools. There is also a separate SDK that works with Metrowerks CodeWarrior.
For 6600 with Visual Studio, it seems the name is wrong (2nd Ed, FP 2 (101MB)). The name of the file to download is s60_sdk_v2_0.zip, though.
For 6630 (e.g., OpenGL ES) with Visual Studio you need the real 2nd Ed, FP2 (142MB). The name of the file to download is s60_2nd_fp2_sdk_msb.zip.
For 6680 get 2nd edition FP3. In general, get the latest SDK (should have more bugs fixed). If you want the application to run on older handsets, that should be no problem as long as you use only APIs that exist also on those phones. For that purpose it may make sense to get the SDK of the phone model you have, for checking which features are there, and the latest SDK that should be in best shape.
For N93, get 3rd edition, Maintenance Release (not the first release of the 3rd ed SDK). Also it seems that most IDE development effort goes toward Carbide, so get the Carbide.c++ IDE. If you have trouble installing the SDK (I had), take a look at the discussion forum for C++ SDK. In general these fora are useful sources of information. Here you will find an example project and slides showing you how to get started on OpenGL ES on N93.
Make that "no tool until now". Here's a tool that allows you to use your own clips instead. It uses Python and PIL (Python Imaging Library). The input is a sequence of images (jpg, bmp, etc.) that can be alphabetically sorted in the right order (blah001.jpg, blah002.jpg, ...), the output is the files handshake_*.yuv, converted to the correct resolutions. Simply replace the default ones with those and start hacking (might want to move the originals to a safe location to be able to recover). The usage instructions are included in the file.