I use a Treo 650, which has a Palm operating system. I'm not sure about the operating system of the Blackberry. If it is Palm compatible, then Smittyware's CacheMate is what you want.
The Blackberry OS is NOT the same as the Palm OS. In fact, the Blackberry fundamentally has a different function as most Palm devices. Palm devices are first and foremost mini-computers, and have a develoment language and OS that is meant for devices that were meant to compute. The TREO series is simply a Palm with wireless communication capability (excellently I might add) attached.
The Blackberry, on the other hand, is the opposite: it is primarily a wireless communication device (later models offer voice/cell capability), but there is beginning to be more development of apps for the Blackberry OS. But its core function is communication with a darn good PDA; the Palm's core function is a PDA and computing, and the Treo adds the comm aspect.
A word of caution: you might find it difficult to find reliable programming for the Blackberry, and depending on your service provider, and who owns the BES server that your email is coming off of (email being the chief reason presumably one carries a BB) you may not be able to load any additional shareware/peripheral software. If you have a BB service/email through your job, your BES server administrator may not want you putting any unauthorized code on a unit that may, ultimately, infect his/her BES or Exchange/Notes/Mail server. Or else your tech support people don't want to have to support it. If you have private service (with, say your local ISP providing your BES server service, or even Yahoo or HotMail providing your BES service) go nuts. I'd be interested in knowing what's out there.
A cludge of a fix might be, if you have Meta Message, to pop your cache files into Word or Adobe PDF and email them to yourself. Meta Message will be able to read them as attachments.