I've recently bought a PSP-2000 (02g) and paired it with the hailed PhotoSmart CR-5400 (twin-slots baby, hawww yeah!) adapter plus 2x Sandisk 8Gb (altogether 16 gigs, on Amazon for... circa $20) and I can't say I'm complaining. It's fast, reliable, it has high capacity and the adapter itself costs only a buck or two so I can get a new one anytime I want if this breaks, although I doubt I'll ever need to remove it from the console.
The only problem with 2000's is the lack of a built-in microphone, but you still *can* get headphones with one if you're desperate to get a pair for Skype or whatever. It's a good trade-in for nearly 100% hack-abillity, a TV out, slim looks and sexy 64 Gigs of RAM.
If you're desperate to buy one WITH a mic, go for the Go (see what I did thar?). 3000's are tricky from what I know, but if you read up on how to recognize which are hackable and which aren't, you'll be fine. Rydian made a cool guide about hacking nearly all PSP's - a good read for a newbie in the PSP town.
As far as memory expansion is concerned, *32Gb is TOPS for 200x, 300x and the Go, for the 100x's I believe it was 16Gb unless firmware updates fixed the issue.*
Recommended first homebrews - Go!Tube, Netfront 4 Beta (HMM Mod)
Recommended Plugins - Mp3Player Lite (by Plum), RemoteJoy, POPSloader