Have a look at one of the m0n0wall forks, pfsense. It supports multi-WAN, but I don't think to the degree you seek.
Thanks for the reply fredg, I took a look at the package, and it seems it does do the failover part fine, Im not sure if it can combine or split the data over the two lines, to give me a greater data rate... I will have to try it out somtime, looking breifly at the blurb, It may work with the load ballancing feature, but im not sure if it split my job, over two 2MB/sec lines?
My next question is probaly quite specialist in nature, will pfsence allow me to use a wifi adapter as a WAN connection? If i wanted to connect to router A and B using two seperate cards, provided they are supported by pfsence, would they be detected as choices for WAN1 and WAN2 inputs? I would be very apreciatvie of any info on this as it would be ideal for what im trying to do.