Hi Deb

What a great question -
I have a few favorites (most are free!)
There are some good conversations for some in the '
resources' section of the forums as well - and then if you check out the
'resources ---> software' section in the directory, here, all of the current listings are products that were recommended by members in the forum.
I don't know that I'd say anything in particular is so much 'required' (aside from Microsoft's Office suite and the like) - I tend to discover new things as my client's needs evolve, but there are always old favorites.
My personal favorites are
PDF995 (you can turn just about anything into a professional looking PDF - this is great for client projects but also for your own practice (marketing materials, etc.)
eFax (rec'v faxes free via email) - the only drawback, of course, is not being able to *send* for free. But there's also FaxZero, which you'll find on
this page - you can send a limited number of free faxes through their site.
Screenhunter5 - you can take snapshots of any part of or all of a webpage. Great for setting up tutorials for clients or showing them samples, etc. (There's also a really cool free product called 'Jing project' that lets you take video of whatever you're doing on your computer, then the file uploads to Jing (scroll down
this page to find the link and listing

) and you just send the link to a client, etc. Also great for giving instruction, etc. (Like a video version of screenhunter)
Is there anything in particular you had in mind?
Truthfully, I think being able to use the net in general to track down fabulous new online technology, etc. is more valuable than even the most expensive software.
One thing I'm really big on with my clients, that isn't software but I think is important for a VA to know how to handle is an enewsletter program - I prefer
Vertical Response because I can design custom templates, etc. they are affordable (no monthly fee) and they offer great stats on campaign results, but there are many other options as well.
I'm sure lots of other members will pitch in their personal favorites here too