With my Linksys you Assign the Starting IP Address for DHCP and then the Number in the Range, for example, 20 IP Addresses and then everything outside of that Range can be used for Static IP Addresses.
I'm fairly sure my 2Wire lets me do the same with the manual setup of the DHCP pool, but I just haven't needed to change the default.
It seems that the netgears are the ones where "defaults" come with everything in the pool, so these, for those with problems, need to have the pool modified.
while this doesn't cover all routers, it's what Merg has put together so far:
Router| Router IP Address| DHCP Pool Range
2Wire HomePortal 1000SW|172.16.0.1|172.16.1.33 – 172.16.1.250
2Wire 2700HG-B Gateway| 192.168.1.254 | 192.168.1.64 - 192.168.1.253
D-Link DIR-825 | 192.168.0.1 | 192.168.0.100 - 192.168.0.199
Linksys WRT320N | 192.168.1.1| 192.168.1.100 - 192.168.1.149
NetGear WGR614v9 | 192.168.1.1 | 192.168.1.2 - 192.168.1.254
NetGear WNDR3700 | 192.168.1.1 |192.168.1.2 - 192.168.1.254