As far as I know, short of becoming a real-estate mogul and buying up every available house/upgrades in the game, or some weird collector fetish (I *have* to purchase or loot a full glass weapons/armor set with every known enchantment on each piece) -- none of which remotely fits the RP for my character -- the game mechanics won't provide an avenue of relief and I'll have to rely on my imagination (which I'm mostly okay with).
In the long run, my character will likely complete the Dark Brotherhood and I figure it'll take lots of septims to get the sisterhood* back up and running the way it should be (* fraternal gender changes are expensive, or so I hear), so I do feel like my growing savings account is serving a purpose.
In the meantime, I do a few other things here and there, such as ....
- Give followers approximately 10-20% of the profit from our adventure(s). Plus leave them with some or all of any of the special gear I gave them. How much of the profit and gear they keep depends upon how much I like them.

- If I use Adrianne's facilities for more than a little touchup, I leave septims in her barrel.
- When Alvor got killed by a dragon, I got an inheritance letter. I felt bad enough that he'd died, getting some of his inheritance made me feel worse; his wife and daughter need the gold more than I do. I visited them for dinner and put the letter, inheritance money, plus 1,000 more septims in their wardrobe. Now every time I visit Riverwood, I stop by and put another thousand into the wardrobe. When I had nothing, they gave me everything. I figure I'll cover Dorthe's apprenticeship until she can make her own sword.
- Any temples or the like that I visit, especially if I use the altar or help myself to some of their supplies, I leave septims. If I take supplies, I leave an amount of gold behind that should more than cover their cost and hassle of having to resupply. (I'm not overly generous though, that'd draw too much attention -- RP, ya know.)
Sooooo, anywaaaz, what imaginative ways have y'all come up with to melt septims out of your RP?