Maybe
If you have an iPhone, MobileMe is worth it if you also need to synchronize contacts/calendars across multiple Macs/PCs, or if you're also not terribly computer literate. The synchronization features are actually quite nice, and some people will like having a single, easy-to-use place for email, photos, online storage, etc., etc.. Now, whether or not all this is worth the price, that's another question. It'll be worth it for some, but not others.
Now, if you're moderately computer-literate, and are willing to go through the hassles, you can get some of the features for free:
- Google and Yahoo have good, free email services, and you can even get free push email accounts from some places. Also, if you use an email provider with server-side filtering/autoforwarding (gmail), you can get push of only selected email.
- There is at least one site that provides free push calendar and contacts to the iPhone. (However, I don't know of any place that provides a way to synchronize multiple iCal/Mail.app/Outlook contacts and calendars, like MobileMe.)
- There are sites that provide free photo sharing (like Google's Picasa). Disk space may be limited, though.
- There are online storage providers that give you a modest amount of disk space for free. Dropbox is one of the best. Not only do they give you 2GB free (with a max file size larger than 2GB), but it works on Macs, PCs, and linux. Oh, and it also auto-synchronizes files between your computers. If you're willing to pay, services like the paid versions of Dropbox or JungleDisk (PC-only, unfortunately) provide cheaper (and possibly more reliable/secure) storage than MobileMe.
Dropbox is really good -- check out their video at: http://www.getdropbox.com