As with most games I played, I tinkered extensively with d20 Modern, developing a slew of house rules. Some where campaign specific; others were meant to be more broadly useful. I posted some of them in threads at EN World, and somehow, through all the various trials and tribulations of that site over the years, they're still there, unlike similar threads posted on the Whizbros forum which are now just memories.
I shelved d20 Modern when my personal 'old school renaissance' began, which included not only the realisation that the games I loved playing when I was younger were still just as playable now, but also the epiphany that I preferred purpose-built games to generic systems. As much as I love tinkering, sometimes it can be more work than seems worthwhile to kit-bash a generic game to get the campaign I want, as in my frustrated attempts at a Great Game campaign and a Zorro campaign, the latter using the execrable d20 Past.
That said, I don't know that I'm entirely done with d20 Modern. I don't tend to hang onto games I don't plan to play again - I lack a strong 'collector' instinct and I'd much rather ditch the dross - but I boxed up all my Modern books and stored them someplace dry.
That same impulse led me to track down those old house rules threads at EN World last week and start transferring them to a page of their own here on Blogger, beginning with a small collection of non-combat feats. I'll continue to transfer the old threads to that page as time allows. Just in case.