Favorite characters are: Picard, Troi, Riker, Kirk, Spock, Janeway and McCoy
For Riker and Troi, I repeat the recommendation of the
Titan series.
For Picard, I recommend
The Buried Age by Christopher L. Bennett, which chronicles Picard's "lost years" between the loss of the
Stargazer and his taking command of the
Enterprise.
I also recommend the anthology
The Sky's the Limit, in particular the stories "'Twould Ring the Bells of Heaven" by Amy Sisson (Troi), "Four Lights" by Keith R.A. DeCandido (Picard), and "Til Death" by Bob Ingersoll & Thom Zahler (Riker).
Another recommendation is the nine-book
A Time to... series, which sets up both
Nemesis and the
Titan series, including what leads Riker to accept a command and Riker and Troi to finally tie the knot.
Picard is the focus also of
Death in Winter by Michael Jan Friedman, the first post-
Nemesis novel, and there's plenty with him in the others in that series:
Resistance by J.M. Dillard,
Q & A by KRAD,
Before Dishonor by Peter David, and
Greater than the Sum by CLB.
Then, for lots of Picard, Riker, and Troi goodness, you have the
Destiny trilogy by David Mack. Lotsa shit happens.
For Janeway, there's an older book,
Fire Ship by Diane Carey, part of the "Captain's Table" miniseries, which focuses entirely on ol' Kathy. And for
Voyager generally, I recommend
Distant Shores, a short story anthology, and the
String Theory trilogy (
Cohesion by Jeffrey Lang,
Fusion by Kirsten Beyer, and
Evolution by Heather Jarman).
For the Big Three of TOS, I strongly recommend the
Crucible trilogy by David R. George III,
McCoy: Provenance of Shadows, Spock: The Fire and the Rose, and
Kirk: A Star for Every Wandering. Also for Spock and McCoy, there's
The Brave and the Bold, a cross-series duology I wrote in 2002 that features those two prominently in both the TOS and TNG portions (and there's plenty of Kirk in the TOS part).
That should keep you going for a while.....