All of these tools have a free option - and I am not associated with them in any way. I'm a web architect and programmer, just working on expanding my marketing muscles after working for marketers big and small for 20+ years. So I don't have quite the marketing intel others may provide here on the forum - but wanted to start giving back a bit.
So here are tools I find essential supporting clients big and small (from Fortune 50 to local nonprofits to independent web marketers).
Evernote (evernote[DOT]com) - My major collection bucket and saves me by being globally available - everything from screen shots, proof of account configurations, PDFs, copies of client emals, etc. I even cc all my client communications to my Evernote account and their notebook. Basic accounts are free, though I have a (very cheap) premium account so I can keep all the digital assets for a project. I usually require clients to create a free Evernote account if they do not already have one, where I then share the project's Evernote folder. Serious CYA if nothing else - and its unstructured enough for folks that find Basecamp too structured.
Unfuddle (unfuddle[DOT]com) - and NetBeans (netbeans[DOT]org). Every project gets an unfuddle account - and a basic account is free. And the projects are all developed using the free NetBeans software. This is for version control - and is essential when dealing with overseas developers. If a contract programmer does not know how to use Subversion or Git for backup and version control -- and isn't willing to check their work into Unfuddle -- take care! If you pay for code - it should be versioned for you and installed on your server from a version. Emailing zips of WordPress plugins is fine (even preferable), but whole sites are something else.
Passpack (passpack[DOT]com) - Perhaps its a pet peeve, but as a web tech it drives me nuts when people email passwords. Not only is it insecure, but email is "discoverable" - as I explain to my corporate clients. If you get involved in a commercial dispute, your passwords could end up delivered to the person suing you. And of course nothing is LESS secure than email, except perhaps bumper stickers. Passpack is a zero-knowledge password repository I use to store and share login passwords. A personal free account is a good start!
IE Tester (www[DOT]my-debugbar[DOT]com/wiki/IETester/HomePage) Developing for multiple versions of IE sucks. Finding out that web code you paid for breaks on IE 6 or IE 7 also sucks. This free (Windows Only) IE tester allows you test your layouts and functionality. This is essential stuff - and FREE for all.
BONUS: Need to debug Flash apps you bought or AJAX code acting flaky? Want to know if a smart user sniffing your web site can download that video for free or without registering? Download the free Fiddler2 (fiddler2[DOT]com) and use the Fiddler Firefox plugin to force all traffic through Fiddler. Its not very user-friendly, BUT - for me it's saved hours of time troubleshooting flash issues, Amazon S3 problems, security issues, and other problems when I couldn't get direct realtime access to the web server logs. It took me two minutes to discover a flash app I had developed for me had a couple of hard-coded directory settings and was ignoring part of the XML config file. It would have taken hours for me to debug manually -- especially since the remote programmer kept saying "it works fine on my server." I did not want to open up my own Adobe C4 and start debugging! I took a quick screen shot of the Fiddler output, sent it back, and it was fixed no questions asked.
If any of this is Greek (or Latin or Klingon) to you, I'd be happy to elaborate :p