I'm using a Mac at work and would like some network shares mounting when i start the computer. Can i use a bash script (or similar) to connect and mount these shares? The shares are from both Windows and Mac servers and we usually connect using IP addresses.
You could check out mount_smbfs, assuming that your network shares are smbfs/cifs.
mount_smbfs [-N] [-o options] [-d mode] [-f mode] [-h] //[domain;][user[:password]@]server[/share] path
I'm not intimately familiar with the OSX startup process, but it's possible you can create your shell-script as a program/folder in /Library/StartupItems or /System/Library/StartupItems
As mentioned on osxbook.com
/etc/rc finally launches /sbin/SystemStarter to handle startup items from locations such as /System/Library/StartupItems and /Library/StartupItems. A StartupItem is a program, usually a shell script, whose name matches the folder name. The folder contains a property list file containing key-value pairs such as Description, Provides, Requires, OrderPreference, start/stop messages etc. You can run SystemStarter -n -D as root to have the program print debugging and dependency information (without actually running anything).