Trying to Get Back on Track(pad), or I Wish There Were a Mouse in My House

Apologies for the lack of posting so far this week; it's not even the usual excuse (lack of time), though that certainly figures in. Rather, this week, it has to do with a computer problem--namely, the trackpad on my MacBook Pro. It just won't, well, track sometimes. I'll move my finger around and around, but to no avail; the arrow just stays in place for a while. It's almost like a very mild version of what it must feel like to be paralyzed in a limb.

The idea has hit me that perhaps the hard drive is getting full, which I realize could affect performance somewhat. To that end, I've been doing the Great Music Purge of '09 whenever I've been on the computer during the past 24 hours. I topped out at 25 days of music, so I've been deleting anything that I already had on a physical CD, saving my iTunes space for things I've gotten through eMusic or Amazon Downloads or the iTunes Store. I'm seeing slightly better performance since I've done that, but the occasional paralysis continues.

So, a quick bleg to my fellow Mac users: Is there anything else that I'm not thinking of which could be causing this problem? A repair is not really in the cards right now, due to budgetary concerns. I also realize that I could just throw down for an actual mouse, bypassing the trackpad altogether, but I'd like some information about that as well: Of the Apple mice, which one have you found to be the best? And how about any other mice that aren't made by Apple but work on Macs--any yays or nays there? Feel free to enlighten me in the comments, as this is driving me nuts; it's taking up to five times as long to do simple tasks, and there are just some things that I can't farm out to the iPhone. Any suggestions would be appreciated.