Borealis
Starting in 2002 Borealis Resin used to offer resin copies of the missing bases from the reissues. Their line included
1972 "RARE HALF" SABERTOOTH BASE - $10
1974 "RARE HALF" ARMOURED DINO BASE - $10
1974 "RARE HALF" SAILBACK BASE - $10
1972 WOOLY MAMMOTH BASE - $30
1972 2-PART ALLOSAURUS BASE - $20

(06/17/09) Note - it appears that Borealis is pretty much unreachable at this time so not sure what the situation is on the bases. I know Cult is out he and several other people have told me they can't get any word on possible return to production.

The 2007 Revell reissues
are out of produciton as of either late 2009 or early 2010
(not sure which, anyone with some hard info, would appreciate it if you would drop me a line)

Cultman's Hobbyshop.

Used to have a resin replacement set for the clear-green parts for the sailback.

In 2008 and 2009 Dencomm offered some really cool calendars.
But nothing in 2010 and I haven't heard a peep about 2011.

Update 9/19/07 -
Moebius Models is not reissuing the Jungle Swamp

Not really an update, as I never really posted it here on the site before.
But I just read where the owner of Moebius has stated that the Jungle Swamp will not be reissued, due to a lack of interest.
read for yourself
Guess they didn't get enough pre-orders to justify the costs.
If you have any on order, then you should check about canceling your order.
Thankfully most reputable sellers do not charge until the items actually come in.
For those who placed bids for the ones that were listed on ebay. You had better see about that before your protection period runs out.