Kippt, what I like about you guys is that you never seem to go away. It looks like you're in it for the long haul, with both feet in (to mix metaphors).
My top 3 basecamp alternatives (minus Trello and in order of preference) would be:
1) Nozbe - http://nozbe.com - Yes, it's a GTD app but you can also upload files and keep stuff organized. Very powerful
2) PBworks - http://pbworks.com - Their pricing is screwed up but there's a lot of flexibility there
3) IQTELL - http://iqtell.com - Promising, I was a heavy user for awhile. No windows app though
There are many other services that are closer clones to Basecamp like Siasto: http://siasto.com but after using them for a few weeks I realize how far behind Basecamp they really are. Siasto didn't seem serious about improving the product either. It was more on autopilot.
Asana: http://asana.com/ Meh. I'm not sure why, but I couldn't get comfortable with it.
What's missing from Basecamp? All my emails in one place, like IQTELL. I log into IQTELL and I get a snapshot of everything that's going on in my life (pretty much). Killer feature.
I bailed from Basecamp. Using Microsoft OneNote for my projects. Pretty good actually. There's a lot to love about OneNote.
Btw,I'm okay with paying a monthly fee, but I'd much rather pay a full year in advance, like with the Microsoft Office 2013 suite. Comes with OneNote and SkyDrive. Very handy.
Hope this helps. I'll keep an eye out for any other questions you might have.
I've tried probably a hundred Basecamp alternatives over the past few years (it's practically a sickness, an obsession) and I still think Basecamp rules. Why? Because I can organize what's in my brain there, and upload files, make notes, export, etc. It's also got silky smooth drag-and-drop action.
It's like Evernote meets a todo. A perfect marriage. I also hate it for that reason. There seems to be nothing else that scratches that itch like Basecamp does. Drives me nuts.
Also, I don't do collaboration though, so the monthly subscription is a bit much for me.
I'll answer any other questions you have. Just reply here. I'm practically an expert on Basecamp alternatives!
P.S. One comes close though, and that's Trello, but Trello doesn't have a good Windows Phone app (yet), and so I won't use it.
I'm already migrating away from Dropbox, after using a pro account for years. They lost my business.
Why? The competitors are better and have more features. SkyDrive integrates tightly with my OneNote, XBox music, Office suite, email and everything else I need. It has features Dropbox doesn't. And it's a better deal.
I don't regret using Dropbox. Not for a second. God knows I've talked them up to all my friends. But performance with them got a bit sketchy and better options are now available.
I'll give you a try this time!