During the last days, I updated the “Virtual 6502” suite of 6502-related tools. They have been around for a while (they may be even the oldest set of 6502 tools on the web still in existence), so they earned a bit of TLC.
Especially the assembler has been extended for a variety of syntax flavors and may therefore still have some function, especially, when it comes to legacy code. (E.g., it should be fully compatible with the original MOS cross-assembler.) However, it’s still a simple assembler, without any support for macros or complex value expressions. But, when it comes to a quick session with some trivial code of mixed or obscure origin (like bits of old and bits of modern code), there may be still a niche.
All the tools now support file-uploads and input via drag&drop, which may be especially useful with the disassembler (as this supports now binary files as a source).
Do two tools make already a suite? Well, there is also the emulator…
(And, BTW, an 6502 Instruction Set Sheet, which is a bit better known.)
For details and links, see this blog post: