The memcached wiki page on WhyNotMemcached indicates MogileFS as the second distributed key/value storage technology that may store objects bigger than 1MB.

Have you thought about memcached?

What exactly are your needs? A really large object cache is much better suited to such things as varnish where latency is not the key to the machine memcached will happily store your 25MB objects, however it will not be noticeably faster than using another thing since additional time is going to be spent moving the item than finding it.