The most recent PS+ post on the PS Blog reveals several SNK arcade games will be releasing as Minis soon. Here's what's coming, July 19th:
Sasuke vs. Commander*
The 6 titles with asterisks are games that were part of the recent, Japan/Asia-only SNK Arcade Classics Vol. 0. With 6 of the collection's 20 games being released as standalone Minis, I guess we aren't likely going to see Vol. 0 itself getting a release in the West. Of the 2 no-asterisk games, Ozma Wars is SNK's first game (and its Wikipedia entry also notes it's the first video game with disparate levels, as well as the first to use a life bar mechanic), and Vanguard is one of the first scrolling shooters (it scrolled both vertically and horizontally).
The same Store update will add 2 SNK NeoGeo titles, Baseball Stars 2 and KoF '95, presumably to the NeoGeo sections of the Store--however, the blog post only notes what looks like a PS3 price, so I can't tell if the titles are coming to the NeoGeo section for the PSP.
The SNK Minis will normally be priced at $3 each, but PS+ subscribers (such as those of us who activated our free 30 days late in the availability period!) will get Guerilla Wars as a subscription-time freebie and all the other titles at 20% off, a savings of 60 cents each.
I'm already backlogged even just on Minis, but thanks to the PS+ discount bit, I think I'll be jumping on the shoot'em-ups in the set: Ozma Wars, HAL 21, Sasuke vs. Commander, and Vanguard. Maybe I'll get Athena, too.