2 ISP on one FreeBSD router

[Piotr Gnyp]

Hi.
Right now we have one ISP, our servers that uses IP from this ISP are
running several services (dns, www, databases, mta etc).
We want to increase stability of our network access by obtaining backup
internet connection from another ISP.
My question is:
Is there a way to configure FreeBSD, so the NATed workstations will use
two ISP at once and in case of one ISP failure the whole traffic will be
put on one connection?