Really depends on the business and your internet usage to be honest. We have about 350 users at head office and we're linking to our UK core network with a pair of resilient Gigabit circuits. We don't push more than 400Mbps on a busy day but anything less than 1Gig isn't worthwhile for a relatively short distance point to point and we (being an ISP) pay a lot less than you will. We'll likely move to WDM on dark fibre for those links fairly soon too. I know much larger organisations who use 100Mbit with a 20 or 40 as backup on cost grounds and works ok for them though.
We (or more accurately I) don't believe in servers in the office, we have thousands of racks of datacenter space, so that's where servers should live (including exchange, AD, file servers), so all access to stuff like that is over the wire rather than local. We do replicate a couple of critical DFS-R shares onto a server in the office as they contain information we would need in the event of a catastrophic failure and could be handy to have a copy but generally, everything stays in the datacenter.
On a semi-related topic, don't do web hosting in your office. Seriously, just don't. It's stupid. You simply aren't as reliable or cost effective in any way as a datacenter and it's a big security risk, most small businesses websites are vulnerable in some way (I should know, we host tens of thousands and the results of internal vulnerability scans against them are ugly) and most small businesses don't use firewall zones effectively - that's a recipe for disaster.
More usefully, our remote offices of around 50-75 users tend to exist on either T3 or 100Mbit ethernet depending on location. Again keep in mind we overbuy as it's cheap for us and everything is accessed over that connection (some places get some local DFS-R data again for specific uses).
Smaller offices tend to get 10Mbit ethernet with a E1 or xDSL backup, we're talking 5 users for most of them but it makes sense to over-provision for us as it leaves us with standardised solutions.
All that is with VOIP, which isn't much of a concern, if you have QOS setup by someone with a clue then VOIP will work over virtually any bandwidth circuit.
