Get MS Office for each Mac
Get CDFinder with a licence for each Mac (it's cheap and I've found nothing better especially for a network)
http://www.cdfinder.de/
(If it's good enough for these people,
http://www.cdfinder.de/praise.html , then I guess it's OK for me)
Get a Mac to use purely as a server (our 733mhz QS works fine for 3 designers). Do what it takes to get a large (300gb+) reliable ATA hard-drive in there (e.g. Sonnet Tempo PCI card). Run the OS system from another separate smaller (10-20gb drive).
Store all your resources on it (Work in Progress folders, Work to Archive folders, logos, fonts, photo-libraries, Excel sheets, contacts, CDfinder database, etc)
Purchase Dantz Retrospect, a number of additional desktop licences (comes with 2 anyway), an external Lacie HD and run a backup script that backs up all the Users folders on each creatives Mac to the servers internal drive then another script that duplicates that big drive to the external hard-drive. This ensures that you have at least one back-up of all centrally stored data and two back-ups of all work on each creative's Mac. Duplicate that external HD to another once every week or two and take it home. Insurance will cover you for most things but your data integrity is in your own hands.
Recommended software: Obviously Adobe CS & Xpress, Suitcase X1 (server maybe), Markzware FlightCheck, MS Office, Stuffit Pro, CDFinder... possibly Filemaker Pro for job tracking etc. 3D software (Carrara, Poser etc), and lastly but not leastly, a decent, sizable and versatile rights-released photo-library (invaluable IMHO)
Don't worry too much about specialised widgets unless you do a lot of specialised design... packaging, publications etc. (If you are doing lots of publications then some custom import xtensions/plug-ins for Word are very handy)
Give some thought to proofing. A decent inkjet & RIP (on a dedicated machine) may be needed plus a fast gutsy A3 B&W laser. A colour calibrator and attention to your colour management is also important.
Establish a simple fool-proof for estimating, billing, booking in & tracking jobs and the time spent on them, whether it's in a couple of ledgers or (recommended) a database which is backed up (see Filemaker Pro).
Distilling PDFs. Put some time & effort into establishing a consistent reliable work-flow for these. We plan to move all of our distilling with hot folders and flight-checking onto a separate machine so people don't have to worry about the local settings on their own machines.
FTP/ISDN. Not much to say here, depends on your clients... could run this from a PC if necessary.
Monitors. If space is not an issue, get decent CRTs with hoods. LCDs are still too expensive when you have to buy 4-6 of them and to my mind, still represent poor value when taking all other costs into account. Save your pennies for extra RAM for the Macs etc.
Training. Don't ignore this. Money spent here will save money down the line especially for people coming from PCs/OS9 etc.
Important! Treat your staff/colleagues well! Have an organised but light-hearted weekly team-meeting just to keep people informed of what's going on and to keep them feeling involved. Have an away-day once a year to discuss future plans, expansion, problems etc. Take 'jollies' once in a while to go to galleries, shows, etc. Keep them inspired, motivated, creative, productive and loyal.