If the SSD is to be your only disk platform, regardless of number of devices, then you have a quandry; how to minimize writes while maintaining reliability and performance.
More specifically, ext4, and 3 for that matter, NILFS, and almost any other modern file system will maintain a journal. Ordinarily this is desirable, however, when dealing with SSD devices it increases the writes performed against the device and thereby reduces its lifespan. One option is to select a conventional IDE, SATA, or other device to which the file system can write its journal. This way one may maintain the benefits of journaling without sacrificing lifespan of the SSD device(s). In the case of ext4 this can be accomplished as:
mke2fs -O journal_dev /dev/external_device then attached to the specific file system as:
mkfs.ext4 -J journal=/dev/external_device. More information can be found in the man page.
An additional feature of file systems to keep in mind when deal with SSD devices is atime. Setting atime on a file system can drastically increase the number of writes to a given device over time. Options for changing this behavior include 'relatime' and 'noatime'.
Since we seem to be focusing on ext4, the kernel documentation on the file system, including its available options, is available for reference here.
Some other options to consider:
noload, as vorbote suggested, and